LIBRARY 

OF    THE 

UNIVERSITY  OF  CALIFORNIA. 
Class 


'     •    ;  :  .;;• 
I    • " " ;  •. .'  ':•    IliH 


Bi 


igp 


IKON  COLUMN  NEAR  KOTAJ*  MINOR,  DELHI,  INDIA. 


ERECTED  B.C.  900* 
Frontispiece^ 


RUSTLESS    COATINGS; 


CORROSION    AND    ELECTROLYSIS 
OF  IRON  AND  STEEL. 


BY 

M.   P.    WOOD, 

Member  of  the  American  Society  of  Mechanical  Engineers,  American  Association 

for  the  Advancement  of  Science;   Consulting  and  Contracting 

Engineer ;  Superintendent  of  Motive  Power,  late 

United  States  Military  Railways. 


FIRST  EDITION. 
FIRST   THOUSAND. 


NEW  YORK : 

JOHN   WILEY   &    SONS. 

LONDON:   CHAPMAN   &   HALL,    LIMITED. 

1904. 


Copyright,  1904, 

BY 
M.  P.  WOOD. 


ROBERT  DRtTMMOND,   PRINTER,   NEW  YORK. 


PREFACE. 


SINCE  the  publication  of  the  papers  "  Rustless  Coatings  for 
Iron  and  Steel/'  in  the  years  1894-1901,  the  author  has  received 
many  requests  from  engineers  and  others  to  present  them  in  a 
more  available  form  than  in  the  Transactions  of  the  American 
Society  of  Mechanical  Engineers  and  in  the  columns  of  the  various 
American  and  foreign  technical  journals.  The  subjects  have  been 
mainly  rewritten  and  new  matter  added  to  bring  them  up  to  date. 
The  characteristics  of  oils,  pigments,  and  paints  that  form  the  prin- 
cipal protective  coatings  for  ferric  and  other  structures  are  given 
at  length  under  their  respective  chapters.  It  is  believed  by  the 
author  that  the  collected  data  will  afford  a  reliable  source  of  in- 
formation of  what  paints  are  composed  and  what  may  be  expected 
of  them.  The  technical  journals  have  given  a  great  deal  of  space 
to  the  subject  of  proctective  coatings  for  metals,  but  the  data  are 
not  always  available  when  comparison  with  some  recent  result  or 
experiment  is  required. 

The  author  acknowledges  the  assistance  afforded  him  in  the  collec- 
tion of  the  data,  by  the  technical  press  and  nearly  two  hundred  other 
sources,  and  he  has,  as  far  as  possible,  given  credit  for  the  same. 

The  subjects  are  so  grouped  in  the  work,  and  so  detailed  in  the 
index,  that  the  busy  man  can  find  the  data  that  will  bear  on  the 
case  in  hand  and  enable  him  to  avoid  some,  if  not  all,  of  the  un- 
favorable results  that  have  attended  previous  applications  of  some 
misleading  trade-mark  mixture.  Most  of  the  analyses  and  tests 
of  the  commercial  pigments  and  paints  have  been  repeated  many 
times  without  any  material  discrepancy  from  the  data  herein  given. 
The  results  from  the  use  of  many  of  these  paints  are  apparent  in  the 
excessive  and  continual  corrosion  of  important  ferric  structures 
everywhere.  He  that  runs  may  not  always  read,  but  he  can  at  least 
see;  hence  should  be  able  to  profit  by  the  experience  of  those  who 
have  preceded  him. 

M.  P.  WOOD. 


122841 


CONTENTS. 


CHAPTER  I. 

Paints,  of  What  Composed.     How  Destroyed.     Classified  as  True  Pigments 

and  Inert  Substances 1 


CHAPTER   II. 
Paint  Statistics  and  General  Character 17 

CHAPTER  III. 
Iron.     Iron  Oxide.     Copperas.     Ochre.     Umber.     Spanish  Brown 26 

CHAPTER  IV. 
Red  Lead.     Litharge 45 

CHAPTER  Y. 
White  Lead.  "Old  Dutch," Quick  Process,  Electrolytic,  and  Sublimed  Lead.     61 

CHAPTER  VI. 
What  Constitutes  a  Good  White  Lead 74 

CHAPTER  VII 
Zinc  Oxide.     Sulphate  of  Zinc.     Lithopone  and  other  Zinc  Pigments 89 

CHAPTER  VIII. 
The  Carbon  Group  of  Pigments      Lampblack 98 

CHAPTER  IX. 

Mineral  and  Artificial  Asphalt.    Coal-tar 103 

v 


vi  CONTENTS. 

CHAPTER  X. 

PAGE 

Asphaltura  Paiuts  and  Carbon  Varnishes.     Fossil  Resins  110 

CHAPTER  XI. 
Baked  Japan  Coatings 119 

CHAPTER  XII. 

Dr.  Angus  Smith's  Anti -corrosive  Water  pipe  Coating  and   other  Water- 
pipe  Dips  and  Coatings 123 

CHAPTER  XIII. 

Graphite.     Amorphous,  Flake,  arid  Acheson's  Electric  Furnace 136 

t 

CHAPTER  XIV. 
Bessemer  Paint  and  Furnace-slag  Pigments 145 

CHAPTER  XV. 

Hydraulic  Cement  Coatings  and  Concrete 149 

CHAPTER  XVI 
Bower-Barff  Coatings 166 

CHAPTER  XVII. 
Galvanizing  Processes 172 

CHAPTER  XVIII. 
Inert  Pigments  and  Adulterating  Substances 184 

CHAPTER   XIX. 
Spirits  of  Turpentine 193 

CHAPTER  XX. 

Bisulphide  of  Carbon.     Tetrachloride  of  Carbon 203 

CHAPTER  XXI. 
Japan  Driers  , 208 


CONTENTS.  vii 

CHAPTER  XXII. 

PAGE 

Flax-plant.     Linseed  and  Linseed -oil 211 

CHAPTER  XXIII. 
Boiling  Linseed-oil.     Processes  and  Experiments 225 

CHAPTER  XXIV. 
Drying  of  Linseed  oil  and  Paint  Coatings 233 

CHAPTER   XXV. 
Tests  for  Linseed-oil  and  Adulterants 240 

CHAPTER  XXVI. 

Substitutes  for  Linseed-oil.      Lucol.      Euphorbium.       Chinese  Wood-oil. 
Japanese  and  Chinese  Lacquers 248 

CHAPTER  XXVII. 

Decay  of  Paint.     Catalytic  Action  of  Pigments.     Caustic  Action  of  Mortar 
and  Cement 261 

CHAPTER   XXVIII. 
Sand-blast  and  Pickling  Processes  for  Cleaning  Metal 271 

CHAPTER   XXIX. 

Paint  Tests.     Toltz's.     Smith's.     Solvay  Cos',  and  others 270 

CHAPTER  XXX. 

Tests  of  Paints  on  Ferric  Structures      Spennrath's  Experiments  on  Paint 

skins 295 

CHAPTER   XXXI. 
Painting  by  Spray 304 

CHAPTER   XXXII 
Mixed  Paints.     Enamel  Paints  and  Baking  Enamels 310 

CHAPTER   XXXIII. 

Corrosion  of  Iron  and  Steel. . . 322 


Vlll  CONTENTS. 

CHAPTER  XXXIV. 

PAGE 

Electrolysis  of  Underground  and  other  Ferric  Substances 370 

CHAPTER  XXXV. 

Marine,  Anti-corrosive,  and  Anti-fouling  Paints  and  Ferric  Alloys 400 

CHAPTER  XXXVI. 

Table  of  Pigments  and  Inert  Substances 408 

Characteristics  of  Metallic  Bases  of  Pigments 410 

Gases  and  Elements  that  Cause  the  Decay  of  Paint 411 

Oxygen  in  Pigments.     Combinations  of  Oxygen,  Carbon,  and  Sulphur 412 

Changes  in  Pigments  Due  to  Atmospheric  Influences 413 

Corrosive  Elements  in  Snow-water,  Smoke,  and  Oils.    Saturated  Air.  414,  415,  416 

Menstruums.     Oils  and  Solvents 417 

Fatty  Acids  and  Solvents. 418 

Proportion  of  Oil  in  Pigment  Pastes 418,  419 

Electro-chemical  Elements 420 


LIST  OF  ILLUSTRATIONS. 


Frontispiece  :  Iron  Column  of  Delhi.     (Page  170.) 

FIG.  PAGE 

1.  Covering  Power  of  Paints 4 

2.  "  "       "       "      5 

3.  Cellular  Formation  of  Wood  (Peeling  of  Paint) 12 

4.  Corrosion  of  Iron.     Atmospheric  Exposure 28 

5.  "         "      "        Single  Application  of  Water 29 

6.  "         "    Tin-plate  in  a  Damp  Cellar 38 

7.  Mill-scale  Corrosion. 40 

8.  Film  of  Red-lead  Paint  incrusted  with  Rust 51 

9.  "      "          "  "    porous  with  Air-bubbles 53 

10.  "      "          "  "     dried  on  a  Glass  Plate 55 

11.  Red  lead,  White  Lead,  and  Zinc  Oxide  Paint-skin 56 

12.  White  Lead.     Corroding  Pot  and  Lead  Buckle 62 

13.  ««          "        Carter's  Process  for  Corroding 68 

14.  "          "         Action  of  Sulphurous  Gases  on  White  Lead 77 

15  and  16.  White  Lead  and  Sublimed  Lead  Coatings  on  Picket  Fence  con- 
trasted    86 

17  and  18.  White  Lead  and  Sublimed  Lead  Painted  Boards 87 

19.  Fossil  Resin.     Section  of  the  Resin Ill 

20.  "         "  (Lithograph) Ill 

21.  Pipe-dipping  Tank 123 

22.  Boiler-tube  coated  with  Graphite  Paint.. . .    141 

23.  Acheson's  Electric  Furnace 143 

24.  Efflorescence  on  Brick  Walls 163 

25  arid  26.  Hot  and  Cold  Process  Zinc  Coating  (Galvanizing) 173 

27.  Table  of  Ziucing  Solutions 176 

28.  "      "  One-minute  Immersions  for  Test  of  Coatings 179 

29.  Inert  Pigments.    Covering  Power 187 

30.  Boxing  Trees,  for  Turpentine,  Old  Method 195 

31.  "  "        "  "  New  Method 201 

32.  Flax-plant  Blossom  from  Jerusalem 212 

33.  ' '  Flower,  Seed-vessel,  Seed  and  Root 214 

34.  Oil-seeds 221 

35.  Mill-scale  Corrosion,  Railway  Viaduct 262 

36.  "  "  Phoenix  Column 262 

37.  Corrosion  of  Steel  Girder,  Washington  Street  Bridge 263 

38.  "         "  Sidewalk  T  Beams 269 

ix 


x  LIST  OF  ILLUSTRATIONS. 

FIG.  FACE 

39.  Sand-blast  Apparatus 271 

40.  Portable  Sand-blast  Machine 272 

41.  Field  Spray  Apparatus  at  Work 305 

42.  Helmet  for  Spray  Painting  or  Sand-blasting 306 

43.  Barrel  and  Hand  power  Spray  Apparatus 307 

44.  Hand  Spray  Apparatus 308 

45.  Power  Paint-mixer 311 

46.  Pipe  Coated  with  Sublimed  Lead 317 

47.  Corrosion  of  a  Laminated  Steel  Girder 333 

48.  "          "  Plate  Girder 335 

49.  "          "  Tee  Rail  in  a  Tunnel 336 

50.  "          "     "       "    on  a  Dock 338 

51.  "        Increased  by  Stress 349 

52.  Diagram  of  the  Corrosibility  of  Metals 354 

53  and  54.  Diagram  of  the  Stress  Corrosibility  of  Wrought  Iron 356 

55.  Diagram  of  the  Stress  Corrosibility  of  Cast  Iron 357 

56.  "         "    "        "  "  "  Cast  Iron  in  Compression 358 

57.  "          "    "        "  "  "  Hard-drawn  Copper  Wire 358 

58    Corrosion  of  Mi'd  Steel  (Ammonia  Chloride  Solution) 364 

59.          "          "  Cast  Iron  (Polished) 364 

CO.          "          "      •'       "    (with  Scale) 365 

61.  "          "  Mild  Steel  (Ammonia  Chloride  Solution) 365 

62.  "          "  Burned  and  Hardened  Steel 365 

63.  "          ••  Burned  Steel  not  Hardened  (with  Scale) 366 

64.  "         "  Annealed  Steel  (Polished) 366 

65.  "          "         "  "     (with  Scale) 366 

66.  "          "  Steel  Burned  but  not  Hardened  (Polished) 367 

67.  "          "  Hardened  Steel  (Polished) 367 

68.  "          "          "  "     (with  Scale) 367 

G9.          "          "  Steel  Burned  and  Hardened  (Polished) 368 

70.  "          "  Sheet  Iron  (Polished) 368 

71.  "          "       l<        •• 368 

72.  "          "      "       "    (with  Scale) 369 

73.  "          "    Peoria  Water  Stand-pipe.     Pitting  of  Sheets 374 

74.  "          "          "          "  "            Course  of  Electric  Currents. ..  376 

75.  "          "          "           "  "             Interior  View  of  Inlet  Pipes. .  376 

76.  "          "  a  12-inch  Cast-iron  Water-pipe 377 

77-  Electrolysis  of  a  4-inch  Cast-iron  Pipe 378 

78.  "  ki  Cast-iron  Water-pipes,  Reading,  Pa 380 

79.  "  "  16-inch  Suction  and  Water  Mains 381 

80.  "  "a  6-inch  Water-pipe,  Providence,  R.  I 382 

81.  "  il  End  Posts  of  a  Swing-bridge  Truss,  Providence,  R.  I 383 

82.  "  "an  8-inch  Water-pipe,  Springfield,  111 384 

83.  "  Lead    Service-pipes    and    Telephone    Cable    Coverings, 
Brooklyn,  N.  Y. 385 

84.  Electrolysis  of  6-inch  Water-pipes,  Kansas  City,  Mo 386 

85.  "  "   Street  Railway  T  Rail,  New  York 386 


RUSTLESS  COATINGS. 


CHAPTER  I. 

PAINTS:    OF  WHAT  COMPOSED,  HOW  DESTROYED,  CLASSIFICATION  AS 
TRUE  PIGMENTS  AND  INERT  SUBSTANCES,  ADULTERANTS,  ETC.* 

WHAT  is  paint?  This  question  can  be  answered  in  a  broad  way 
by  saying:  It  is  any  liquid  or  semi-liquid  substance  applied  to  any 
metallic,  wooden,  or  other  surface,  to  protect  it  from  corrosion  or 
decay,  or  to  give  color  or  gloss,  or  all  of  these  qualities,  to  it. 

A  better  definition  would  be,  that  paint  is  a  compound  of  a  pig- 
ment and  a  liquid,  usually  applied  to  any  surface  with  a  brush,  for 
the  purpose  of  protection,  or  to  secure  artistic  effects;  which  liquid, 
after  undergoing  certain  changes,  in  part  mechanical,  or  chemical, 
or  both,  has  the  power  of  holding  the  pigment  to  the  coated  surface. 
It  is  evident  that  the  latter  definition  would  also  include  those  com- 
pounds which  are  applied  to  many  surfaces  either  hot  or  cold  as  a  bath, 
rather  than  by  a  brush,  solely  as  a  matter  of  convenience  or  rapidity; 
and  particularly  so  when  metallic  members  of  large  size,  or  with 
intricate  and  hidden  parts,  are  to  be  protected. 

The  essentials  of  a  good  paint,  for  whatever  use  intended,  are: 

First. — That  it  shall  adhere  firmly  to  the  surface  over  which 
it  is  spread,  and  not  chip  or  peel  off.  It  must  be  non-corrosive  to 
the  material  it  is  used  to  protect,  as  well  as  to  itself  under  long  periods 
of  atmospheric  exposure  and  chemical  changes.  It  must  form  a 
surface  hard  enough  to  resist  frictional  influences,  yet  elastic  enough 
to  conform  to  all  changes  of  temperature,  or  with  a  coefficient  of 

*  Excerpts  from  a  paper  by  the  author  presented  at  the  Detroit  meeting 
(June,  1895)  of  the  American  Society  of  Mechanical  Engineers,  and  forming 
part  of  Volume  XVI,  paper  number  637,  of  the  Transactions. 


2  ESSENTIALS  OF  A   GOOD  PAINT. 

elasticity  approximately  as  near  the  material  it  covers  as  possible. 
It  must  be  impervious  to  and  unaffected  by  moisture,  atmospheric 
or  other  influences  to  which  the  structure  may  be  exposed. 

Second. — That  it  shall  work  properly  during  its  application — a 
property  which  depends  largely  upon  the  relative  amounts  of  pig- 
ment and  liquid.  The  natures  of  both  pigment  and  liquid  also  have 
influences  that  govern  results. 

Third. — That  it  shall  dry  with  sufficient  rapidity.  This  func- 
tion depends  mostly  upon  the  vehicle  or  liquid  used  with  the  pig- 
ment, though  the  pigment  has  in  many  cases  an  influence,  as  will 
be  seen  further  on. 

Fourth. — That  it  shall  have  proper  durability,  which  is  a  func- 
tion both  of  the  pigment  and  liquid.  And  as  the  question  of  cost 
is  in  many  cases  the  governing  factor  in  the  selection  of  a  paint, 
the  question  of  durability  may  be  regarded  as  the  most  important 
one  of  the  list.  It  should  be  understood,  however,  that  a  paint  can 
be  durable  per  se,  and  not  be  protective  in  the  strict  sense  of  the 
word,  as  can  be  illustrated  in  the  case  of  a  good  paint  applied  to  the 
surface  of  a  sheet  of  iron  coated  with  rust.  The  liquid  element  in 
the  paint  will  not  absorb  or  neutralize  the  corrosion  which  it  covers, 
but  will  dry  regardless  of  it,  and  permit  the  destruction  of  the  metal 
to  progress  beneath  its  coat. 

Fifth. — Covering  power,  by  which  is  meant  the  power  of  a  pig- 
ment so  to  cover  the  surface  to  which  it  may  be  applied  that  its  pro- 
tection from  decay  is  not  only  assured,  but  that  the  minimum  amount 
of  paint  shall  effect  this  purpose. 

The  covering  power  is  also  used  to  express  the  power  of  a  pigment 
to  protect  the  oil  from  decay,  in  which  case  a  large  amount  of  pigment 
and  a  small  amount  of  oil  are  used.  This  description  of  paint  dries 
more  or  less  "flat,"  the  pigment  being  exposed  to  the  weather  and 
held  in  place  by  the  thin  film  of  oil.  It  is  thought  by  many  master 
painters  that  this  is  the  most  durable  and  best  paint  for  general  use. 
On  the  contrary,  paints  that  dry  with  a  gloss  have  a  large  amount 
of  oil  and  a  small  amount  of  pigment,  in  which  case  the  oil  covers 
and  protects  the  pigment. 

It  may  be  used  to  express  the  amount  of  color  upon  the  surface; 
as,  generally,  if  a  surface  has  plenty  of  color  upon  it  the  covering 
power  is  said  to  be  good.  To  illustrate  this  definition :  If  an  iron- 
oxide  paint  is  proportioned  so  that  the  ratio  between  the  pigment 
and  the  oil  is  by  weight  50  per  cent  of  pigment  and  50  per  cent  of  oil 


PAINTS,  COVERING  AND  COLORING  POWER.  3 

when  the  paint  is  ready  for  spreading,  and  the  pigment  consists  of 
30  to  40  per  cent  of  iron  oxide,  the  covering  power  will  be  said  to  be 
good;  but  if  the  same  proportions  of  50  per  cent  ratio  between  the 
pigment  and  the  oil  be  had,  in  which  the  iron  oxide  is  only  5  per  cent 
of  the  pigment,  the  covering  power  would  be  called  poor;  and  so  it 
would  be  in  the  case  where  10  per  cent  of  pigment  and  90  per  cent 
of  oil  were  used.  If  in  the  two  latter  cases  the  oil  contained  large  or 
liberal  amounts  of  volatile  diluents,  the  appearance  of  the  surface 
would  indicate  a  deficiency  in  the  covering  power  of  the  paint. 

The  covering  power  is  also  commonly  expressed  in  the  amount 
of  surface  which  a  given  weight  of  paint  will  cover.  A  good  iron- 
oxide  paint  will  cover  nearly  twice  as  much  surface  as  white  or  red 
lead.  The  specific  gravity  of  the  paint  also  is  to  be  considered  in 
the  definition  of  this  power.  The  lightest  paints  have  the  most 
covering  power.  White  lead  is  about  6.4  times  as  heavy  as  water; 
iron  oxide  5  times;  yellow  ochre  3^  to  4  times,  etc.,  etc.  With  this 
variation  it  is  manifestly  almost  an  impossibility  to  get  the  same 
number  of  particles  of  the  same  size  out  of  the  same  weight  of  different 
materials. 

Fig.  1  represents  the  covering  power  of  a  number  of  paints  and 
inert  pigments. 

The  refracting  power  of  light  has  much  to  do  with  an  under- 
standing of  this  covering  power  of  paint.  The  greater  the  refracting 
power  of  the  pigment  is  over  that  of  the  oil,  the  better  will  be  the 
covering  power.  The  index  of  refraction  of  air  is  1  degree;  water, 
1.34;  linseed-oil,  1.48;  glass,  1.50  to  1.55;  silica,  1.55;  feldspar,  1.54; 
whiting,  1.65;  chrome-yellow,  3.00;  vermilion,  3.20,  etc.  There 
is  no  exception  to  the  rule  that  the  finer  the  state  of  division  to  which 
any  pigment  is  reduced,  the  better  will  be  its  covering  power.  Sul- 
phate of  lime,  barytes,  feldspar,  silica,  talc,  whiting,  etc.,  are  all  of 
low  refractive  power,  and  of  themselves,  independent  of  this  refrac- 
tive quality,  do  not  constitute  good  pigments,  though  when  mixed 
with  the  metallic  pigments  and  ground  together  in  the  oil  the  result 
is  a  pigment  of  good  covering  power,  almost  as  good  as  the  best  one 
of  the  combination.  For  instance,  80  per  cent  of  sulphate  of  lime 
and  20  per  cent  of  zinc  white,  form  a  pigment  almost  as  good  as  all 
zinc  white,  and  10  per  cent  of  white  lead  and  90  per  cent  of  talc  care- 
fully ground,  give  a  very  satisfactory  result  so  far  as  relates  to  the 
covering  power;  but  all  of  the  above  and  other  kindred  compositions, 
while  improving  the  covering  power,  are  to  be  classed  as  adulterants, 


4 


PAINTS,  REFRACTING  OR  COLORING  POWER. 


the  use  of  which  is  objectionable  so  far  as  durability  and  protective 
power  are  concerned. 

The  covering  power  is  due  to  two  qualities.  For  instance  lime 
whitewash  has  very  little  covering  power  until  it  becomes  dry. 
Barytes  covers  well  as  a  water  paint,  because  the  water  leaves  it  as 
a  dry  powder  on  the  coated  surface.  But  barytes  covers  poorly  in 


FIG.  1. — Covering  power  of  paints. 

oil,  because  the  oil  remains  with  it,  and  the  light  reaches  it  through 
the  transparent  film  of  oil. 

Prof.  Von  Bezold's  experiments,*  from  which  I  quote,  illustrate 
how  lime,  barytes,  white  lead,  and  other  crystalline  pigments,  when 
mixed  in  oil,  become  more  or  less  translucent,  and  therefore  do  not 
color  the  surface  that  they  cover. 

*  Von  Bezold.  "  Theory  of  Color."  L.  Prang  Co.  Condict's  "  Painting  and 
Painting  Materials." — The  Railroad  Gazette. 


PAINTS,  REFRACTING  OR  COLORING  POWER. 


"If  a  small  glass  test-tube  be  partly  filled  with  powdered  glass, 
the  powder  will  appear  white,  and  it  will  be  impossible  to  see  through 
it,  but  as  soon  as  water  is  poured  into  the  tube,  the  powder,  to  a 
certain  degree,  becomes  translucent.  By  substituting  turpentine  for 
the  water,  the  degree  of  translucency  is  materially  increased.  If  a 
small  quantity  of  sulphuret  of  carbon  is  added  to  the  turpentine,  a 
liquid  is  obtained  that  reflects  (bends)  the  light  about  as  powerfully 
as  glass.  If  some  of  this  liquid  be  poured  upon  the  powder  in  the 
test-tube,  the  powder  will  disappear,  and  light  passes  through  the  tube 
as  freely  as  though  no  powder  were  present. 

If  a  solid  glass  rod  be  immersed  in  such  a  liquor  (or  a  mixture  of 
olive-oil  and  oil  of  cassia),  it  will  appear  as  if  the  rod  only  reached  to 
the  surface  of  the   liquid.     Within 
the    liquid  the  rod  cannot  be  seen 
(Fig.  2). 

It  is  shown  by  these  experi- 
ments that  the  presence  of  one 
transparent  body  within  another 
is  only  detected  by  the  eye  when 
the  two  differ  in  their  power  of 
refracting  light. 

Many  white  substances  are  white 
because  they  are  in  fine  particles. 
A  white  lily  is  white  because  it 
consists  of  little  cells  which  reflect 
all  kinds  of  light,  again  and  again, 
until  it  reaches  the  eye  from  some 
part  of  its  surface.  Water  be- 
comes white  when  it  is  broken  into 

fine  drops,  as  in  a  waterfall  or  on  the  crest  of  waves.  White  lead 
and  zinc  owe  their  whiteness  to  their  dense,  fine,  powder-like  condi- 
tion, and  transparent  glass  becomes  white  when  finely  pulverized." 

As  stated  before,  the  finer  the  pigment  is  subdivided,  whether  as 
a  paste  which  is  afterward  thinned  with  oil  or  volatiles  to  a  consist- 
ency to  spread  with  a  brush,  or  is  ground  in  the  oil  direct  (a  process 
that  all  pigments  will  not  endure  without  injury  to  their  color — the 
scarlet  lead  chromate,  for  instance)  to  the  proper  consistency  to 
spread,  the  better  will  be  its  covering  power. 

An  ounce  of  lampblack,  because  of  the  minuteness  of  its  par- 
ticles, will  cover  more  surface  in  an  effectively  protective  maimer 


FIG.  2. 


6  PAINTS,  REFRACTING  OR  COLORING  POWER. 

than  any  known  pigment,  and  one  part  lampblack  and  nine  parts 
sulphate  of  lime  by  weight,  give  most  excellent  results  in  covering 
power.  Prussian  blue,  the  scarlets,  lakes,  and  others  of  what  can 
be  called  "the  fugitive  colors/'  on  account  of  their  tendency  to  fade 
out,  possess  the  light-dispersing  power  which  deceives  the  eye  as  to 
their  covering  power,  when  in  reality  for  actual  covering  as  protective 
substances  they  are  absolutely  worthless.  These  colors  should  be  de- 
nominated stains  rather  than  paints;  for  generally  the  only  measure 
of  protection  from  decay  or  corrosion  which  accompanies  their  use 
is  solely  from  the  oil  or  liquid  with  which  the  color  is  mixed. 

The  designing  of  a  paint,  for  whatever  purpose,  necessarily  in- 
cludes the  qualities  already  mentioned,  viz.:  adhesion  and  elas- 
ticity, working  qualities,  drying  qualities,  durability,  covering  power. 
The  other  quality,  the  cost,  cannot  be  ignored,  and  will  be  duly  con- 
sidered later,  as  well  as  what  pigments  to  use  for  the  intended  purpose. 
All  pigments  do  not  contain  all  of  the  above  qualities.  The  question 
naturally  arises :  Is  it  necessary  for  a  pigment  to  be  pure  and  unmixed 
with  inert  substances,  or  can  a  certain  amount  of  these  be  mixed 
with  the  pigment  without  detriment  to  it? 

Experiments  of  long  duration  lead  to  the  conclusion  that  the 
oxides  of  iron,  lead,  manganese,  and  other  strong  pigments,  can  be 
mixed  with  large  amounts  of  these  inert  substances  without  detriment, 
and  generally  to  the  manifest  improvement  of  the  paint  as  a  pro- 
tective agent  on  many  structures,  notably  wooden  or  composite  ones. 
A  single  illustration  will  suffice  to  make  this  apparent.  Oxide  of 
iron  is  one  of  the  strongest  of  pigments  in  covering  power.  If  one 
ounce  of  this  pigment  be  spread  in  two  coats  over  a  given  surface, 
say  two  square  feet,  so  that  the  surface  be  completely  hidden,  and 
the  job  be  declared  a  satisfactory  one  so  far  as  covering  power  is  con- 
cerned, and  in  the  second  case  an  ounce  of  the  same  oxide  of  iron  be 
mixed  with  three  ounces  of  barytes,  kaolin,  gypsum,  etc.,  and  this 
paint  be  spread  over  two  square  feet  of  surface  as  before,  it  is  obvious 
that  the  amount  of  color  per  unit  of  surface  will  be  the  same  in  both 
cases ;  but  in  one  case  there  is  four  times  as  much  pigment  as  in  the 
other,  and  in  the  second  case  three-fourths  of  the  paint  would  be 
inert  material.  For  railway  cars  and  wooden  structures  the  dura- 
bility of  these  paints  would  be  in  favor  of  the  second  case,  as  well  as 
the  cost  of  the  paint.  The  pigment  in  this  case  is  the  life  of  the  paint, 
and  protects  the  oil  from  the  decay  incident  to  oxidation  from  atmos- 
pheric exposure. 


PAINTS,  COVERING  AND   COLORING  POWER.  1 

Oxide  of  iron  is  practically  unchanged  after  centuries  of  exposure. 
It  induces  and  promotes  oxidation  in  all  organic  substances  with 
which  it  is  brought  into  contact,  and  in  nearly  all  metallic  bodies. 
In  an  oxide-of-iron  paint  it  is  the  oil  which  decomposes,  it  being 
the  organic  matter.  The  decomposition  is  due  to  the  exposure  to 
the  elements  aided  by  the  oxidizing  power  of  the  oxide  of  iron  pig- 
ment mixed  with  the  oil.  This  statement  holds  true  only  where 
there  has  been  no  chemical  change  or  combination  between  the 
pigment  and  the  liquid. 

Whiting,  sulphate  of  lime,  barytes,  kaolin,  silica,  feldspar,  and 
talc  are  the  principal  inert  substances  used  in  pigments.  Whiting, 
gypsum,  and  barytes  are  the  best  of  the  list;  the  others,  grinding 
greasy,  are  hard  to  grind,  or  of  a  nature  readily  decomposed  by 
water,  are  objectionable.  Barytes,  from  its  great  weight,  is  objec- 
tionable as  a  paste  or  prepared  paint.  Its  use  as  an  adulterant  is 
given  in  Chapters  VI  and  XVIII.  The  sulphate  of  lime  (gypsum)  is 
no  doubt  the  best  of  the  inert  substances  to  mix  with  any  pigment, 
all  things  considered.  It  should  be  thoroughly  hydrated.  As  high 
as  45  per  cent  by  weight  of  this  substance  can  be  mixed  with  50  per 
cent  of  sesquioxide  of  iron  for  a  pigment.  Many  of  the  oxide-of-iron 
paints  are  made  by  ignition  of  copperas,  and  a  notable  amount  of 
sulphuric  acid  is  usually  left  in  the  oxide  which  the  heat  has  failed  to 
drive  off.  From  2  to  5  per  cent  of  carbonate  of  lime  is  added  to  neutral- 
ize the  free  acid,  changing  it  to  sulphate  of  lime.  In  these  proportions, 
the  pigment  really  consists  of  50  per  cent  of  oxide  of  iron  and  50  per 
cent  of  inert  material,  all  by  weight.  Any  oxide-of-iron  paint  which 
contains  hydrated  oxide  or  free  SO2  will  deteriorate  rapidly  by  oxidiz- 
ing the  liquids,  while  any  free  S02  will  retard  the  drying  of  the  paint. 

A  good  paint  prepared  for  spreading  in  ordinary  temperatures 
upon  wooden  or  composite  structures  has  the  ratio  by  volume  of 
about  one-third  pigment  and  two-thirds  oil  or  liquid.  The  practice 
upon  one  of  the  leading  railways  of  the  United  States,  where  the 
materials  purchased  for  paints  amount  to  over  $300,000  yearly,  is 
to  allow  75  per  cent  of  pigment  and  25  per  cent  of  oil  by  weight,  for 
the  paints  applied  to  cars  and  wooden  structures. 

Experiments  determine  that  the  most  durable  paints  are  those 
which  contain  a  large  amount  of  pigment  per  unit  of  surface ;  and  that 
pigment  is  the  best  which  is  strong  enough  of  itself,  or  with  a  proper 
proportion  of  inert  material,  to  allow  liquid  enough  to  be  added  to 
it  to  flow  and  work  well  with  the  brush  when  applied. 


8  PAINTS,  MECHANICAL  INJURY. 

Destruction  of  Paint. 

The  destruction  of  paint  may  be  from  eight  causes :  First,  mechan- 
ical injury;  second,  the  action  of  deleterious  gases;  third,  chemical 
action  between  the  pigment  and  the  vehicle  or  liquid ;  fourth,  chemical 
action  between  the  body  covered  and  the  paint,  either  the  pigment 
or  the  liquid;  fifth,  the  action  of  light;  sixth,  peeling;  seventh,  destruc- 
tion by  cleaning;  eighth,  water. 

Many  master  painters  and  manufacturers  claim  that  the  destruc- 
tion caused  by  cleaning  and  the  action  of  water  are  the  worst  of  the 
above  causes.  This  is  true  so  far  as  paint  applied  to  wooden  structures 
is  concerned,  but  has  no  relation  to  the  causes  which  effect  the  destruc- 
tion of  paint  applied  to  iron  or  steel  structures.  As  most  of  the 
above  destructive  agents  are  common  to  all  structures  (wooden, 
metallic,  or  composite)  which  depend  in  a  greater  or  less  degree  for 
their  preservation  from  decay  or  corrosion,  upon  paint  (under  which 
name  all  paints,  oils,  varnishes,  japans,  and  surfacers  are  classed),  it 
may  not  be  amiss  to  discuss  briefly  each  of  these  causes  in  detail  before 
citing  the  destructive  agencies  which  relate  solely  to  the  corrosion 
of  metallic  structures,  the  prevention  of  which  will  require  the  con- 
sideration of  other  preservative  methods  than  paints,  or  which  may 
be  used  in  connection  with  paint  to  secure  the  best  protective  results. 

First. — Mechanical  injury  to  wooden  structures  is  not  a  serious 
cause  of  deterioration  of  paint.  Near  the  seashore  the  wind  and  sand 
have  the  effect  of  a  sand-blast,  which  cuts  away  the  paint  rapidly,  and 
in  this  case  the  more  elastic  the  paint,  the  less  will  be  the  mechan- 
ical injury.  This  sand-blast  action  is  quite  as  effective  on  ferric 
structures,  and  as  generally  they  are  of  a  more  important  character 
than  the  wooden  cottages  and  minor  buildings  on  the  seacoast,  its 
action  must  be  guarded  against.  If  the  paint  coating  is  of  a  soft, 
spongy  nature  it  will  resist  the  sand-blast,  but  will  absorb  moisture 
from  the  air,  and  hasten  either  the  oxidation  of  the  paint  or  the 
metallic  surface  which  it  covers. 

A  further  injury  to  metallic  structures  can  be  classed  under  the 
head  of  mechanical,  viz.:  that  arising  from  the  expansion  and  con- 
traction of  the  various  parts  from  the  atmospheric  changes  which 
are  constantly  going  on,  changes  ranging  from  40  degrees  F.  to  150 
degrees  F.  not  being  unusual.  It  is  an  impossibility  to  proportion  a 
paint  compound  so  that  its  coefficient  of  elasticity  will  be  the  same  at 
all  temperatures  as  that  of  the  metal  it  covers.  It  may  be  possible 


PAINTS,  MECHANICAL  INJURY.  9 

to  do  this  at  some  temperature  at  or  between  60  degrees  and  90  degrees 
F.,  or  even  between  +40  degrees  F.  and  90  degrees  F.;  but  that  any 
paint  in  the  class  of  commercial  colors  will  do  this  at  all  temperatures 
is  the  tale  of  the  salesman.  It  may  be  argued  that,  these  changes 
coming  from  the  external  surface  of  the  paint  and  being  transmitted 
through  its  coating,  it  will  be  the  first  to  adjust  itself  to  the  new  or 
varying  relation  between  the  metal  and  the  paint,  and  so  will  work  to 
the  advantage  of  the  paint  in  making  the  change,  this  being  in  ordi- 
nary cases  a  gradual  one.  If  the  paint  is  of  an  elastic,  close-clinging 
material,  and  not  a  hard,  vitreous  one,  the  claim  will  hold  good. 

The  compounds  which  most  closely  partake  of  this  nature,  will 
be  spoken  of  hereafter.  An  addition  to  this  problem  will  be  had 
when  the  strains  due  to  the  action  of  wind,  the  passage  of  railway 
trains,  and  those  due  to  changes  of  a  sudden  and  vibratory  character, 
together  with  the  action  of  snow,  hail,  and  water  driven  at  high 
velocities,  are  added  to  the  temperature  changes.  These  strains 
necessarily  come  to  the  metal  first,  and  whatever  changes  occur 
in  the  bars  by  the  strain,  the  paint  must  accompany  them.  As 
these  strains  are  generally  of  a  vibratory  or  percussive  character, 
it  can  easily  be  seen  why  they  should  be  classed  in  the  list  of 
mechanical  injuries.  In  fact,  they  are  a  succession  of  blows  which 
the  structure  must  absorb,  withstand,  and  extinguish  within  itself  or 
its  connections;  the  structure  then  returning  to  its  normal  condition, 
the  paint  or  other  protective  covering  must  accompany* it,  instead 
of  loitering  by  the  way  and  being  grounded  or  "left"  in  the  chain  of 
operations. 

Second. — The  action  of  deleterious  gases  is  very  familiar  to  those 
who  have  studied  paints  and  protective  compounds.  Sulphuretted 
hydrogen  is  one  of  the  most  common  and  active  of  these  gases,  and 
is  formed  in  excessive  amounts  wherever  coal  is  distilled  for  illuminating 
gas.  Sulphurous  acid  fumes  also,  being  disengaged  in  the  combus- 
tion of  coal  in  the  many  arts,  transportation,  and  manufacturing 
processes  of  the  day;  gases  engendered  in  workshops,  being  of  a 
compound  character  carrying  ammonia,  carbonic  acid,  nitric  acid, 
and  other  fumes,  are  active  agents  of  corrosion  to  metallic  bodies, 
also  to  the  paint  compounds  that  cover  them.  (See  Analysis  of 
Smoke,  Chapter  XXXVI.) 

Third. — Chemical  action  between  the  pigment  and  the  vehicle. 
This  is  an  exceedingly  important  field  of  inquiry,  and  largely  an 
unknown  one.  Many  of  the  siccative  and  other  oils  which  are  in 


10  PAINTS,  CHEMICAL  ACTION  ON. 

common  use  for  paints  are  capable  of  saponification.  It  is  well 
known  that  soda  and  potash  are  not  the  only  substances  which  com- 
bine with  fats  to  produce  soap,  and  that  almost  any  of  the  bases  can  be 
combined  with  the  fatty  acids  of  nearly  all  oils  to  make  soap,  hence 
we  have  iron  soap,  lead  soap,  zinc  soap,  manganese  soap,  etc.  Many 
pigments  are  simply  oxides  or  hydrates,  in  the  same  way  that  soda 
and  potash  are,  and  it  is  strongly  suspected  that  they  combine  with 
the  oil  to  form  soaps,  in  which  case  it  will  be  evident  that,  after  the 
paint  has  been  left  on  the  surface  for  a  number  of  years,  instead  of  a 
pigment  held  to  the  surface  by  the  liquid  and  which  has  undergone 
certain  changes  called  "drying,"  it  is  in  reality  a  new  chemical  body 
consisting  of  the  constituents  of  the  liquid  combined  with  the  pig- 
ment, or  in  other  words,  it  may  be  a  soap. 

Fourth. — Chemical  action  between  the  body  covered  and  the 
paint,  either  the  pigment  or  the  vehicle.  The  chemical  changes 
which  may  or  do  take  place  between  the  pigment  and  the  liquid 
as  set  forth  in  Article  III,  can  be  supplemented  here  to  embrace 
those  paints  which  contain  pigments,  one  or  more  of  which  give 
up  oxygen  or  break  down  in  the  presence  of  organic  matter — the  oil 
or  liquid  of  the  paint.  Hydrated  oxide  of  iron  (iron-rust)  oxidizes 
organic  matter  (the  oil)  and  gradually  destroys  it.  Oxide-of-iron 
paints  of  all  kinds  gradually  grow  darker  with  age  from  the  oxidation 
of  the  oil,  this  oxidation  progressing  until  either  the  paint  cracks 
and  falls  off  as  a  scale  on  any  mechanical  disturbance,  or  is  washed 
away  in  the  process  of  cleaning  or  by  the  action  of  storms.  Chromate 
of  lead,  bichromate  of  potash,  the  chlorates,  magnanese  dioxide, 
red  lead,  and  a  number  of  other  pigments  also  possess  this  oxidizing 
power  to  a  great  degree. 

Fifth. — The  action  of  light.  The  action  of  light  as  a  bleaching 
element  is  well  known  in  almost  all  fields  of  human  industry;  but 
the  chemical  changes  which  occur  between  the  pigment  and  the 
liquid  are  not  well  understood,  this  action  being  furthermore  compli- 
cated by  the  different  temperatures  to  which  the  coated  surface 
may  be  exposed,  and  aided  by  the  effects  of  sea  air  or  fumes  from 
various  manufactories.  We  know  that  certain  pigments  fade  upon 
exposure,  whether  applied  to  metallic  or  other  structures.  The 
pigments  which  contain  organic  coloring- matter  from  coal-tars, 
dyewoods,  etc.,  fade  more  rapidly  than  those  which  have  a  metallic 
base;  but  it  has  never  been  established  that  the  bleaching  of  the  paint 
in  all  cases  detracts  from  its  durability. 


PEELING  OF  PAINTS.  11 

Sixth. — Peeling.  Paints  vary  greatly  in  their  power  to  adhere  to 
either  metallic,  wooden,  or  other  surfaces;  notably  zinc  white,  which 
peels  under  almost  any  condition  or  from  any  surface  to  which  it 
may  be  applied.  There  is  no  other  pigment  which  possesses  this 
property  in  so  marked  a  degree,  and  it  is  difficult  to  assign  any  reason 
why  it  should  peel  so  badly.  A  possible  cause  is  that  the  zinc  white 
combines  with  the  oil  used  in  the  paint  and  forms  one  of  the  com- 
pounds known  as  metallic  soap,  this  particular  one  being  zinc  soap, 
a  hard,  brittle,  non-adhesive  substance,  easily  removed  by  mechanical 
injury,  water,  and  in  the  process  of  cleaning,  etc.  Galvanized  iron 
possesses  the  property  of  causing  almost  any  paint  applied  to  its 
surface  to  peel;  in  fact,  it  is  one  of  the  worst  substances  to  cover 
with  a  pigment  in  a  satisfactory  manner.  Experiments  made  by  a 
leading  railway  company  in  the  United  States,  in  which  a  number 
of  the  best  pigments  in  use  by  that  company  for  all  descriptions  of 
railway  work  were  tried  upon  galvanized-iron  car-roofs  and  other 
galvanized  work,  cornices,  etc.,  showed  at  the  end  of  three  years 
that  but  one  of  the  list  was  in  any  manner  satisfactory,  and  this  one 
was  a  patented  compound  with  bisulphide  of  carbon  as  the  vehicle. 
Ordinary  trade  colors  are  of  the  most  unreliable  nature  when  applied 
to  galvanized  iron  exposed  to  the  trying  conditions  of  railway  service. 
Various  reasons  have  been  given  for  this  peculiar  action  of  paint 
upon  galvanized  iron.  One  of  the  most  plausible  is  that  the  use  of 
sal-ammoniac  in  the  process 'of  galvanizing  causes  the  formation  of 
a  thin  film  of  the  basic  chloride  of  zinc  on  the  surface  of  the  metal 
being  galvanized,  which  material,  being  of  a  hygroscopic  nature, 
acts  as  a  repellant  to  prevent  the  close  adherence  of  the  paint  to  the 
metal,  and  the  pigment  dries  as  a  skin  over  it.  Sheet  zinc  does  not 
hold  some  kinds  of  paint.  Sheet  lead  also  is  difficult  to  cover,  and 
paints  which  take  tin  and  lead  will  not  always  adhere  to  zinc.  As  a 
general  rule,  the  strong  oxide  paints  take  these  metals  better  than 
talc,  ochre,  and  the  earthy  pigments.  No  positive  general  statement 
can  be  given,  and  the  problem  of  the  adaptability  of  paint  to  a  metal 
to  prevent  peeling  still  needs  study  for  each  application.  Paints  ap- 
plied in  cold  weather,  and  which  are  exposed  to  a  frost  while  drying, 
will  always  peel,  unless  the  paint  is  warmed  to  about  120  degrees  F. 

Another  fruitful  cause  of  the  peeling  of  paint  is  when  the  several 
coats  are  successively  applied  before  the  foundation  or  preceding 
coat  has  thoroughly  dried,  the  result  being  that  the  liquid  in  the 
outer  or  last  applied  coats,  softens  those  previously  applied.  The 


12 


PEELING  OF  PAINTS. 


resulting  mass,  containing  a  notable  amount  of  the  more  volatile 
elements  of  the  liquid,  beginning  to  dry  from  the  outside  surface, 
forms  a  thin  but  hard  or  vitreous  surface  which  retards  the  further 
evaporation  of  the  volatiles  and  prevents  the  access  of  oxygen  from 
the  air,  which  is  necessary  in  the  process  of  drying.  If  the  surface 
thus  covered  has  been  painted  while  at  a  low  temperature  or  during 
a  damp  or  foggy  atmospheric  condition,  and  soon  after  there  is  a 
marked  rise  in  the  temperature  or  a  fall  in  the  hygroscopic  condition 
of  the  atmosphere,  then  the  paint  is  liable  to  peel  at  once,  or  soon 
after  the  change.  This  effect  is  hastened  where  the  coating  is  a 
heavy  one,  or  one  hard  to  spread  by  reason  of  the  earthy  or  inert 
substances  in  the  pigment,  or  if  benzine  has  been  used  as  a  drier. 

As  a  general  rule,  the  more  substances  that  enter  into  a  paint, 
either  as  pure  pigments,  inert  substances,  or  in  the  composition  of 
the  liquid,  the  more  liable  it  is  to  peel.  A  small  amount  of  fish  or 
animal  or  non-drying  vegetable  oils,  though  oxidized  by  the  addition 
of  metallic  salts  and  used  in  connection  with  linseed  or  other  siccative 
oils,  also  hastens  and  provides  for  the  certainty  of  the  peeling. 

The  peeling  of  paint  from  wooden  surfaces  is  very  common, 
particularly  if  applied  on  unseasoned  lumber  that  contains  moisture 

and    air    in    the    cellular    formation  of 

the  wood  as  shown  by  the  cut.  The  air 
and  moisture  in  the  cells  expand  upon 
a  slight  rise4  in  temperature,  and  in  their 
efforts  to  escape  through  the  dried  paint- 
skin,  push  it  up  in  the  form  of  blisters 
that  contain  the  condensed  moisture, 
and  results  in  the  peeling  of  the  paint 
in  blisters  or  in  strips. 

A  pigment  composed  of  a  number 
of  substances,  the  different  materials  of 
which  by  themselves  would  form  the 
basis  of  a  good  paint,  when  combined 
together  with  the  liquid,  necessarily 
undergo  a  different  chemical  action  than 
of  the  several  members  of  the  pigment 

paint.  would  have   done  had  they  been  used 

alone.  This  chemical  action  is  furthermore  complicated  by  the  combina- 
tions going  on  in  the  liquid,  which,  formed  of  a  number  of  different 
elements  that  act  and  react  upon  one  another,  and  mixed  with  the 


PAINTS,  DESTRUCTION  BY  CLEANING.  13 

heterogeneous  pigment,  develop  a  series  of  chemical  actions  in  the  mass, 
the  weaker  element  of  which,  either  the  mineral  or  the  organic,  is  the 
first  to  break  down  or  change,  the  decay  of  which  hastens  the  decom- 
position of  the  others  and  releases  the  bond  between  the  paint  and  the 
surface  over  which  it  is  spread,  and  the  peeling  process  is  effected. 

That  these  chemical  changes  exist  in  the  above  stated  case  cannot 
be  denied,  but  have  not  been  well  accounted  for.  The  fact  remains, 
however,  that  certain  paints  peel,  and  though  analysis  of  the  peeled 
portion  may  reveal  nothing  to  indicate  the  reason  for  the  peeling, 
it  is  seldom  possible  to  get  a  sample  of  the  original  paint  applied,  to 
compare  its  constituents  with  the  peeled  sample,  and  the  cause  is 
relegated  to  the  hidden  drawer  of  the  paint-shop,  near  which  some 
.scapegoat  can  be  found  to  bear  the  burden  of  failure.  (For  other 
notes  on  the  peeling  of  paint,  see  Index.) 

Seventh. — Destruction  by  cleaning.  This  cause  of  the  deteriora- 
tion and  destruction  of  paint  applies  more  particularly  to  wooden 
structures,  railway  cars,  and  kindred  objects,  than  to  those  of  a 
metallic  character.  It  may  be  sufficient  to  say  we  do  not  wash 
down  an  iron  bridge,  roof-truss,  or  steamship,  with  a  view  to  its  pre- 
senting a  clean  face  for  inspection  and  painting.  Almost  all  the 
binding  materials  of  dried  paints  and  varnishes  are  more  or  less  acted 
upon  by  caustic  and  carbonated  alkalies,  and  but  little  of  the  soap 
in  the  market  is  free  from  these  substances.  The  detergents  sold 
for  cleaning  are  all  mixtures  of  sal-soda  and  caustic  substances  with 
lime,  pumice,  and  other  inert  materials,  and  the  more  effective  they 
are  for  removing  dirt,  the  better  they  are  for  the  destruction  of  the 
paint.  If,  in  the  economy  of  domestic  household  matters,  two  re- 
movals are  equal  to  one  fire,  then  it  may  be  cited  with  equal  force 
that  two  good  scrubbings  with  any  washing  compound,  and  most  of 
the  soaps  of  commerce,  applied  with  a  stiff  brush,  will  be  equal  to  the 
next  painter's  bill  to  restore  matters  to  their  pristine  state.  Aside 
from  the  element  of  cost,  it  is  no  doubt  the  better  practice,  so  far 
as  the  ultimate  preservation  of  any  metallic  structure  is  concerned,  that 
it  should  be  washed  clean  with  some  of  the  detergent  compounds  of 
the  day,  in  a  very  weak  solution  to  remove  the  dirt,  then  sponged 
with  a  liberal  amount  of  clean  water,  then  be  allowed  to  dry  thor- 
oughly before  the  new  paint  is  applied;  but  I  must  confess  as  an 
engineer,  that  the  above  method  of  painting  is  rare,  and  that  the  rule  is 
for  the  paint  to  be  put  on  regardless  of  cleaning  the  old  coat,  and, 
like  Charity,  trust  it  to  cover  the  sins  beneath. 


14  WATER-TESTS  FOR  PAINTS. 

Eighth.  —  Water.  The  destructive  action  of  water  upon  paint 
applied  to  structures  of  any  material,  either  upon  their  internal  or 
external  surfaces,  is  very  strong,  and  will  rank  next  in  destructive 
qualities  to  the  detergent  soap  and  scrubbing-brush.  Inside  painting 
lasts  longer  than  outside,  principally  because  it  is  less  exposed  to 
the  action  of  water.  Direct  experiments  show  that  dried  linseed 
and  other  siccative  oils,  without  pigment,  are  not  resistant  or 
water-repellent.  When  the  oil  is  well  dried,  the  application  of  water 
always  causes  the  oil  to  assume  a  shrivelled  appearance,  showing 
that  it  has  absorbed  moisture  and  expanded,  and  disintegration  has 
commenced.  If  the  exposure  be  long  continued,  the  whole  coating 
of  dried  oil  will  slump  away  from  the  surface  over  which  it  is  spread. 
Rain-water,  from  the  sensible  amount  of  ammonia  that  it  carries, 
increases  this  destructive  action  on  the  dried  oil,  and  the  slow  wasting 
away  of  good  paints  containing  pigments  best  known  to  resist  aging 
influences,  and  which  have  been  hardened  by  time,  can  be  attributed 
to  this  action. 

The  ordinary  test  by  master  painters,  of  the  ability  of  an  oil  or 
paint  to  resist  moisture  is  to  coat  a  surface,  usually  of  glass,  and 
when  well  dried,  to  immerse  it  in  water  for  a  few  hours  and  note  the 
changes  in  color  and  integrity  of  the  paint. 

Dr.  Dudley's  experiments  for  the  Pennsylvania  Railroad,  on  the 
action  of  water  upon  paints,  are  interesting  from  the  care  which  was 
exercised  in  making  them  and  recording  the  results.  Several  sam- 
ples of  a  paint  designed  for  use  upon  cars  and  wooden  structures 
were  made  with  raw  linseed-oil  and  a  very  small  amount  of  japan  ;  the 
same  liquid  being  used  for  all  the  samples  with  varying  amounts  of 
pigment,  all  the  proportions  being  by  weight.  Two  coats  of  these 
paints  were  spread  upon  glass,  and  allowed  to  harden  for  two  to 
three  weeks.  These  samples  were  then  placed  side  by  side,  and  a 
small  portion  of  the  surface  of  each  covered  with  a  globule  of  water. 
This  globule  was  covered  to  prevent  evaporation,  and  then  allowed 
to  stand  for  twelve  to  fourteen  hours. 

No.  1  was  the  linseed-oil  and  japan  alone. 
"    2         "      same  liquid  90  parts,  pigment  10  parts. 
"    3         "  "          80  "  20      " 

"    4         "  "          70  "  30      " 

"    5         "  "          60  "  40      " 

"    6         "  "          50  "  50      " 

"     7        "  "          40  "  60      " 


-g 


WATER-TESTS  FOR  PAINTS.  15 

When  the  proportions  are  higher  than  liquid  40  parts  and  60  of 
pigment,  the  paint  will  not  spread  well  with  a  brush  if  the  liquid  is 
linseed-oil  and  the  pigment  has  the  specific  gravity  of  ordinary  oxide- 
of-iron  paints. 

At  the  end  of  the  period  named,  the  behavior  of  the  samples 
was  as  follows:  No.  1  coating  was  found  to  have  cleaved  off  the 
glass  and  had  become  shrivelled  wherever  the  water  had  touched 
it.  Apparently  the  dried  linseed-oil  had  soaked  up  water,  much  as 
a  sponge  acts  as  an  absorbent.  On  allowing  the  water  to  evaporate, 
the  coating  dried  down  again,  but  not  uniformly,  and  was  apparently 
weakened  in  texture. 

No.  2  showed  the  same  characteristics. 

No.  3  showed  the  same,  but  in  a  less  degree. 

No.  4  did  not  cleave  off  the  glass,  but  showed  where  the  water 
had  stood. 

No.  5  showed  a  spot  in  the  same  way,  but  in  a  less  degree  than 
No.  4. 

Nos.  6  and  7  showed  but  very  little  action. 

It  can  be  noted  that  here  linseed-oil  dried  for  some  two  months 
absorbed  less  water  than  freshly  dried  oil,  while  very  old  dried  oil 
lost  this  absorbent  quality  and  became  almost  water-repellent. 

To  successfully  design  a  paint  which  will  resist  all  of  the  previously 
named  destructive  agencies,  is  a  difficult  matter.  The  field  is  an  enor- 
mous one  to  cover  and  but  little  positive  knowledge  has  yet  been 
obtained,  though  the  investigators  and  experiments  have  been  legion, 
and  the  literature  on  the  subject  embraces  volumes.  Time  is  an  essen- 
tial factor  in  the  test  of  the  qualities  of  a  paint,  and  if  the  experimenter 
is  required  to  wait  five  or  ten  years  to  determine  the  merits  of  any 
paint,  or  what  effect  a  slight  modification  of  the  proportions  has  upon 
any  one  or  more  of  the  eight  destructive  agencies  heretofore  stated, 
a  life  could  be  spent  and  possibly  no  conclusion  reached. 

Experiments  are  numerous  in  the  field  of  designing  a  water-proof 
coating  to  be  applied  over  the  pigment  which  has  been  found  to  pos- 
sess the  most  preservative  qualities,  independent  of  the  water-repellent 
features,  but  the  goal  is  not  yet  reached.  How  effectually  a  thin 
coating  of  the  proper  material  can  protect  the  surface  of  a  paint 
which  it  covers,  can  be  seen  in  the  lettering  of  old  sign-boards,  which 
is  perhaps  an  example  of  the  most  durable  paint  of  which  we  have  any 
record. 

This  protective  effect  is  explained  by  the  well-known  fact  that 


16  PAINTS,  WHAT   IS  REQUIRED. 

lampblack  is  one  of  the  best  water-repellents  known,  that  it  is  practi- 
cally indestructible  by  oxidation  or  acids,  and  being  per  se  of  an  oily 
or  greasy  nature,  when  mixed  with  a  pure  oil  (linseed  in  these  cases), 
and  being  in  a  measure  elastic,  it  has  effectually  preserved  the  surfaces 
and  not  allowed  the  water  to  reach  the  underlying  coats  of  white  lead. 
Having  set  forth  the  general  character  of  what  a  paint  should  be 
for  the  purpose  of  protecting  structures  from  decay  or  corrosion, 
and  having  indicated  the  most  effective  causes  which  provoke  or 
promote  the  destruction  of  the  object  and  its  protector,  it  may  not 
be  amiss  to  speak  more  definitely  upon  those  materials  which  enter 
into  paint  compounds  which  yield  the  best  results  in  general  practice. 
These  results  are  based  upon  the  experience  thus  far  at  hand  as 
recorded  or  accepted  data,  and  not  the  hypothesis  of  some  person  or 
persons  whose  single  or  joint  lives  may  be  too  short  a  period,  as  com- 
pared with  the  life  of  the  structure  they  are  striving  to  protect  from 
decay,  to  realize  the  meritorious  features  of  their  experiment. 


CHAPTER  II. 
PAINTS:     STATISTICS  AND  GENERAL  CHARACTER. 

THERE  are  in  the  United  States  at  the  present  date  (1903)  about 
420  firms  engaged  as  manufacturers  and  compounders  of  pigments, 
pastes,  and  paints  of  all  grades,  representing  a  yearly  output  equiva- 
lent to  about  90,000,000  gallons  of  mixed  paints,  that  cost  not  far 
from  $65,000,000. 

This  represents  about  570,000  short  tons,  and  would  cover  with 
one  coat  900,000  acres  or  1400  square  miles  of  surface,  requiring 
50,000  painters  to  spread  it. 

The  following  details  are  the  average  amounts  of  the  principal 
pigments  used  in  the  United  States  for  the  years  1898  to  1902: 

Iron  oxide,  23,500  short  tons.     Value  $10.75  to  $11.00  per  ton. 

"        7,000       "       "  "         9.00  for  mortar  colors. 

White  lead  ground  in  oil,  85,100  short  tons.     Value  5.25  to  5.50  cents  per  pound. 
"     dry 25,100      "       "  "     4.70  to  4.90     "         "       " 

"       "      imported 300  to  700  tons. 

Red  lead 11,100  short  tons.          "     5.30  to  5.50     "         "      " 

"     "     imported 400  to  800  tons. 

Litharge 11,000  short  tons.          "    5.30  to  5.80     "         "      " 

"         imported 40  to  350  tons. 

Orange  mineral 10,200  tons.  "    7.25  to  7.50     "         "      " 

"  "       imported  500  to  700  tons. 

Zinc  oxide 40,200  tons.  "     4.00  to  4.25     "         "      " 

"       "   imported  in  oil  16,000     "     Dry,  250  tons. 

Flake  graphite 1450  tons  ) 

Amorphous  graphite 2500     "    >•  Value  5.50  to  6.25     "         "      " 

Acheson's  "       30     "    ) 

Imported  graphites  of  all  grades  average  from  10  to  12  times  the  amounts 
produced  in  America. 

Ochres  of  all  grades  were  produced  in  13  different  States,  Pennsylvania  fur- 
nishing over  one-half  of  the  entire  output  of  14,200  to  14,500  short  tons.  Value 
$6.50  to  $7.00  per  ton. 

Imported  ochres,  7,700  to  8,000  tons.     Value  $7.70  to  $7.90  per  ton. 

Spanish  brown,  principally  from  Maryland,  600  to  650  tons.  Value  $17.70 
to  $18.00  per  ton. 

Approximately,  the  United  States  produced  248,600  short  tons  of  the  above 
pigments,  paints,  and  pastes,  against  53,300  "  "  imported. 

17 


18  PAINTS,  GENERAL  CHARACTER  OF. 

What  proportion  of  these  amounts  were  really  applied  for  the 
preservation  of  metallic  structures  on  shore  or  afloat,  it  is  difficult  to 
determine ;  but  one-fourth  part  may  be  taken  as  the  yearly  allowance 
to  cover  the  effects  of  corrosion  in  progress  in  some  degree  in  about 
every  metallic  structure  that  meets  the  eye,  and  may  be  considered 
as  the  annual  contribution  to  the  coffers  of  corrosion. 

The  general  tenor  of  paint-trade  literature  would  lead  the  layman 
to  infer  that  each  one  of  the  above  noted  420  firms  was  the  right 
and  only  one  that  could  or  did  furnish  the  special  and  imperishable 
paint  that  he  was  in  search  of.  The  customer  who  is  in  search  of 
facts  as  well  as  paint  will  find  some  of  the  former  in  Chapters  Vr 
XXXII,  XXXIII,  XXXIV,  XXXV  that  may  guide  him  in  selecting 
the  latter. 

The  greater  part  of  the  mixed  pastes  and  paints  of  the  day  are 
adulterations,  and  are  presented  to  the  public  in  these  forms  the 
better  to  conceal  the  actual  composition  of  the  pigments  and  to  save 
oil;  also  to  disguise  the  quality  of  the  vehicle,  as  in  the  form  of  a 
paste  or  paint  it  requires  chemical  skill  and  time  to  analyze  a  sample 
of  either.  This,  while  applying  in  general  to  the  mixed-paint  house 
colors,  does  not  exempt  large  quantities  of  mixed  paints  sold  exclu- 
sively as  ferric  protective  coatings. 

There  are  at  the  present  day  as  pure  brands  of  linseed-oil,  red 
and  white  lead,  lampblack,  and  other  pigments  manufactured  as 
any  ever  made.  Possibly  they  are  better  on  the  average  than 
those  made  one  hundred  years  ago;  but  there  are  more  that  are  a 
great  deal  poorer,  and  rendered  more  so  by  adulterations  of  the 
most  barefaced  character.  There  is  a  great  advantage  in  the  use  of 
prepared  paste,  as  the  quality  of  the  vehicle  required  to  bring 
it  to  paint  can  be  positively  known,  also  the  driers  used,  and  what 
amount  of  these  is  necessary  to  meet  any  condition  present  at  the 
time  and  place  of  applying  the  coating, — details  that  in  most  cases 
cannot  be  known  in  advance  or  by  the  paint-compounder,  unless, 
as  is  too  often  the  case,  he  makes  but  one  kind,  and  fits  it  for  the  con- 
templated duty  by  the  difference  in  price  and  the  gullibility  of  the 
customer. 

There  are  many  reputable  and  responsible  manufacturers  of, 
and  dealers  in  mixed  paints,  who  will  and  do  give  a  statement  of 
the  materials  they  use  in  a  brand  of  mixed  paint  and  the  reason  there- 
for. But  they  do  not  sell  pure  linseed-oil,  under  a  fancy  trade-mark, 
for  19  cents  a  gallon,  nor  a  paint  for  40  cents  a  gallon,  that  if  the 


PAINTS,  GENERAL   CHARACTER  AND   COST.  19 

given  materials  were  only  approximately  pure,  would  cost  nearer  a 
dollar.  Neither  do  they  expect  it  to  be  spread  with  a  stiff,  hard 
brush  to  enable  it  to  cover  a  large  area  as  a  recommendation  for  its 
cheapness  and  superiority. 

It  costs  as  much  for  labor,  brushes,  scaffolds,  and  other  items  to 
spread  a  poor  paint  as  a  good  one.  On  railway  bridges,  viaducts, 
and  structural  ironwork  painted  in  situ,  it  costs  for  the  painters' 
labor  about  twice  the  cost  of  the  paint  and  in  many  cases  four  times 
as  much, — depending  upon  the  character  and  amount  of  scaffolds 
or  ladder-work. 

This  assumes  that  a  reliable  paint  is  used  that  costs  about  a  dollar 
a  gallon,  that  will  cover  from  300  to  400  square  feet  of  surface  for 
the  first  coat,  and  from  500  to  600  square  feet  for  the  second  or  a 
repainting  coat.  In  the  latter  case  the  surface  covered  may  be 
less,  or  the  same  as  for  the  first  coat,  all  depending  upon  the  labor 
of  scraping  or  the  condition  of  the  surface  of  the  old  coating,  whether 
scraped  or  not.  .  Obviously,  the  claim  that  a  paint  can  coat  1000 
square  feet  of  surface  or  more,  and  prove  as  durable  as  those  covering 
less  surface,  as  above,  is  not  sustained  in  practice,  though  it  is  always 
possible  to  get  a  doctored  result  with  any  paint,  good  or  bad.  Paint- 
films — that  is,  the  oil  covering  the  atoms  of  the  pigment — are  only 
from  -^-Q-  to  ToW  m°h  'm  thickness,  whatever  the  size  of  the  pigment- 
atoms.  It  stands  to  reason  that  a  thick  coating  of  the  vehicle  will 
better  protect  the  pigment-atom  than  a  thin  one.  If  the  pigment- 
atom  is  susceptible  in  any  degree  to  atmospheric  influences,  it  will 
be  less  affected  with  a  heavy  coating  of  the  vehicle  than  with  a  thin 
one.  A  thin  coating  usually  implies  that  the  oil  has  been  reduced 
in  density  to  render  it  easier  to  spread,  and  to  be  spread  over  a  larger 
area,  by  the  use  of  a  larger  quantity  of  solvents,  either  turpentine  or 
benzine,  than  is  necessary  with  any  good  quality  of  either  raw  or 
boiled  linseed-oil. 

Red-lead  paint,  from  the  large  amount  of  oil  in  it  and  its  great 
specific  gravity,  spreads  over  a  large  area,  and  it  is  these  features 
that  cause  it  to  run  or  crawl  on  vertical  or  slightly  inclined  surfaces, 
particularly  in  the  first  coat. 

A  like  result  follows  the  use  of  flake-graphite  pigments.  The 
atoms  of  this  variety  of  graphite,  on  account  of  their  smooth  surface 
and  low  coefficient  of  friction,  appear  to  slide  around  in  the  vehicle 
before  it  dries  enough  to  retain  them  in  position  when  spread.  The 
silica  and  barytes  frequently  mixed  with  such  pigments  to  give  a 


20       ESSENTIAL  ELEMENTS  FOR  SECURING  GOOD  RESULTS. 

frictional  resistance  to  overcome  this  gliding  are  almost  as  non- 
absorbent  or  repellent  of  the  oil  as  the  flake-graphite  atom,  and 
have  a  greater  specific  gravity  to  crowd  them  downward. 

While  the  following  excerpts  *  and  the  author's  views  are  in  the 
main  more  applicable  to  railway  bridges  and  structural  ironwork 
than  to  house-painting  or  the  many  minor  ferric  or  composite  surfaces 
that  require  painting,  possibly,  more  for  appearance  than  protection 
from  corrosion,  yet  it  is  quite  apparent  that  there  is  too  much  poor 
paint  spread  in  both  cases.  The  frequent  failures  or  inferior  results 
of  all  kinds  of  paint  applied  to  all  classes  of  structures  can  be  attributed 
to,  not  only  the  paint  and  the  manner  and  time  of  applying  it,  but  to 
the  improper  preparation  of  the  surface  to  be  covered.  ^ 

This  is  particularly  the  case  in  regard  to  bridge  and  structural 
painting.  Particular  emphasis  is  laid  upon  this  point  by  every  author- 
ity and  writer  on  the  subject  in  the  technical  literature  of  the  master 
painters  and  engineering  associations'  debates  and  reports.  Every 
specification  for  painting,  bristles  with  clauses  prescribing  what  shall 
or  shall  not  be  done,  and  still  the  fact  remains  that  there  are  more 
failures  than  even  indifferent  successes,  especially  on  work  painted 
at  the  shops  before  shipment.  The  causes  for  the  irregular  and  indif- 
ferent results  are  not  difficult  to  ascertain.  They  are  the  improper 
application  of  the  paint  to  dirty,  greasy,  moist  or  chilled,  rusty  or 
mill-scaled  surfaces.  No  marked  improvement  in  these  uncertain 
results  can  be  had  until  the  same  importance  is  attached  to  the  "paint 
question,"  not  only  on  paper,  but  in  the  actual  supervision  of  the 
painting  in  all  of  its  stages,  as  is  given  to  the  minutest  construction 
details. 

How  carelessly  this  essential  is  generally  performed  even  by 
engineers  in  charge  of  large  bridges  and  other  structures  is  seen  in 
the  instance  of  an  inspecting  engineer  who  reports  visiting  the  work- 
shops to  observe  the  condition  of  the  metal  after  being  manufactured 
into  structural  work  and  during  the  painting  process.  "The  metal 
had  been  housed,  but  there  were  many  rust-spots  on  the  web-plates, 
also  on  the  angles,  which  were  covered  with  scale.  The  metal  was 
being  cleaned  by  putty  knives  and  whisk-brooms.  Steel  brushes  were 
sometimes  used  (presumably  as  long  as  the  visitor  was  present).  // 
there  was  anything  unusual  in  this  method  of  cleaning  at  the  shops  it 
was  on  the  part  of  thoroughness.  (The  italics  are  the  author's.)  After 

*  Excerpts  from  Engineering  News,  June  6,  1895. 


PAINTS,  ENGINEERS'  RESPONSIBILITY  FOR  A  GOOD  RESULT.  21 

cleaning,  the  plates  still  showed  thin  yellow  rust-spots,  that  showed 
plainly,  but  of  a  darker  color  after  coating  with  oil.  The  oil  was 
scraped  from  some  rust-spots  under  the  oil  on  dry  girders  in  the 
yard,  and  the  yellow  color  of  rust,  so  often  found,  was  developed." 

It  is  to  be  regretted  that  this  engineer's  views  of  what  constitutes 
a  thorough  preparation  of  the  ferric  surface  for  its  coat  of  paint  is 
not  an  exception,  but  the  rule  in  more  than  nine-tenths  of  the  struc- 
tural manufacturing  establishments.  Notwithstanding  their  claims 
to  pre-eminence  in  their  profession,  they  have  yet  to  learn  how  to 
protect  what  they  create;  and  that  they  are  either  incapable  of  this, 
or  indifferent  to  it,  the  present  condition  of  the  ferric  structures  of  the 
day  is  an  unanswerable  evidence. 

If  the  superiors  do  not  understand  the  importance  of  the  proper 
preparation  of  the  surface  to  be  covered,  or  the  character  of  the  paint 
and  manner  of  applying  it,  or  give  them  the  same  or  more  con- 
sideration than  they  attach  to  other  matters  of  construction,  it  will 
be  next  to  impossible  for  the  inspector  or  master  painter  to  enforce 
good  work.  It  requires  a  more  determined  stand  on  the  part  of  those 
in  charge  of  this  branch  to  ensure  good  work,  than  in  any  other  part 
of  the  construction  details.  Until  the  head  officers  are  zealous  enough 
to  care  something  about  the  condition  of  the  work  after  it  has  left 
the  shop,  and  the  men  actually  in  charge  of  the  painting  are  given  to 
understand  that  they  will  have  the  unquestionable  backing  and  sup- 
port of  their  superiors  in  any  stand  they  take  against  the  present  so- 
called  practical  methods  of  structural  painting  by  unscrupulous 
contractors,  just  so  long  will  their  work  show  their  neglect  in  the 
rapid  progress  of  corrosion,  that  will  not  need  scraping  the  surface  of 
the  coating  to  find. 

The  low  grade  of  labor  available  for  the  painters'  gang  has  much 
to  do  with  the  generally  unsatisfactory  results  obtained.  Painting 
can  be  slighted  and  still  present  a  creditable  surface  that  will  pass 
inspection  more  easily  than  any  other  branch  of  hand  labor  connected 
with  bridge  or  structural  ironwork.  Painting  is  as  hard  in  muscular 
requirements  as  light  blacksmithing  or  the  vise-work  of  a  machinist, 
and  the  painter  is  not  addicted  to  wasting  his  elbow-grease  to  work 
out  his  paint  over  any  larger  area  than  he  can  well  avoid.  In  con- 
tract painting  this  element  is  noticeable,  as  there  will  often  be  25 
to  30  per  cent  of  difference  in  the  areas  coated  by  different  workmen 
upon  the  same  job,  and  the  eye  can  hardly  detect  the  difference. 
The  regular  bridge  inspector  in  charge  of  the  work  at  the  shop  is  so 


22         CLEANING  SURFACES  PREPARATORY  TO  PAINTING. 

crowded  with  miscellaneous  duties,  that  the  inspection  of  the  painting 
is  usually  a  farce,  even  if  the  quality  of  the  paint,  the  weather,  and 
other  conditions  are  favorable  to  secure  a  first-class  result. 

These  features  are  particularly  apparent  if  red  lead  is  the  paint 
used  for  the  shop  coat,  as  any  want  of  care  in  keeping  it  continually 
well  stirred  up  in  the  paint-pot  by  the  paddle-stick  (not  by  the  brush) 
to  prevent  its  " setting"  is  almost  undetectable,  and  the  want  of  care 
here  governs  the  durability  of  all  of  the  subsequent  coatings.  The 
use  of  lampblack  with  red  lead  in  a  paint  coating,  while  it  delays 
the  quick  " setting"  of  the  coating,  does  not  prevent  the  rapid  settling 
of  the  pigment. 

Probably  the  best  results  could  be  obtained  if  the  man  or  firm 
who  pays  for  the  completed  structural  work  appointed  his  or  their  own 
inspector  to  attend  to  this  branch  of  the  work  with  the  distinct  under- 
standing that  his  orders  were  to  be  strictly  enforced,  and  that  his 
endorsement  on  the  bill  rendered  was  necessary  before  payment  of 
the  same.  This  would  ensure  the  proper  preparation  of  the  surface, 
and  secure  careful  attention  to  the  before-mentioned  necessaries ;  and 
he  alone  could  be  held  responsible  for  the  final  results.  In  general, 
railway  bridges  that  have  the  several  coatings  of  paint  applied  under 
the  direct  supervision  of  one  of  the  railway  company's  own  corps  of 
engineers  have  proven  to  be  better  protected  against  corrosion  than 
the  structures  painted  either  by  contract  or  by  the  most  prominent  of 
the  construction  firms,  who,  as  a  rule,  are  more  anxious  to  get  the  work 
out  of  the  shop,  than  for  its  future  fate. 

The  pickling  of  structural  iron  with  dilute  acids  to  remove  the 
mill-scale,  as  done  in  some  classes  of  ship  and  boiler  work,  has  met 
with  many  objections.  These  objections  are  primarily  the  cost  of 
the  process  compared  with  a  rush  coat  of  something  denominated 
paint. 

When  pickled  and  brushed  clean  of  scale,  the  metal  must  be  copi- 
ously washed  in  water  and  then  dried  if  possible  in  the  sun,  or  artifi- 
cially in  a  warm  room  or  oven,  and  then,  whether  machined  or  not, 
be  coated  with  the  first  coat  of  paint.  Tf  a  few  hours  elapse  before 
applying  the  coating,  the  surfaces  will  begin  to  acquire  the  thin 
blush  coating  of  red  rust,  as  described  in  Chapter  III. 

The  use  of  the  sand-blast  at  the  final  stage  of  the  machining  proc- 
esses will  effectually  remove  the  dirt  and  scale,  but  the  machine-grease 
must  be  soaked  free  with  turpentine  and  thoroughly  wiped  off,  and 
not  allowed  to  dry  down  again. 


PAINTING  AT  THE  MILL.  23 

Both  the  pickling  and  sand-blast  processes  cost  money,  patience, 
and  grim  determination  to  apply,  but  the  result  in  having  a  properly 
cleaned  surface  for  the  foundation  of  the  protective  coatings  has 
been  proven  in  hundreds  of  cases  as  the  only  sure  method  to  reduce 
the  maintenance  expense  of  the  structure.  (See  Chapter  XXVIII, 
Sand-blast  and  Pickling.) 

Many  engineers  are  advocating  the  plan  of  having  a  coating  of 
either  boiled  oil  or  paint  applied  to  the  iron  or  steel  at  the  mill  as 
soon  as  possible  after  it  has  left  the  rolls  or  hammer,  and  while  the 
metal  is  hot.  The  hot  part  is  the  only  part  to  commend.  All  metal  as 
it  leaves  the  rolls  or  hammer  has  a  tough,  thick  or  thin  (as  the  case 
may  be)  coat  of  loose  or  partly  loose  scale  that  adheres  for  the  time 
being,  but  on  a  short  exposure  to  the  air  with  a  few  changes  in  tem- 
perature, due  to  mill  or  storehouse  conditions,  releases  its  tension 
and  is  ready  to  fall  off  whenever  handled,  as  in  the  course  of  loading 
and  transportation.  No  amount  of  brushing  that  any  mill  employe 
would  or  could  give  to  the  metal  in  its  hot  or  half-cold  condition  would 
remove  this  scale,  and  if  the  painter  was  present  with  his  pot  of  oil  or 
paint,  it  would  get  on  over  scales  and  all,  and  no  ordinary  inspector 
could  prevent  it,  or  be  in  any  way  sure  that  the  contract  requirements 
had  been  complied  with  in  regard  to  the  removal  of  the  scale  or  the 
composition  of  the  coating. 

The  mill  coating  is  exposed  during  its  application  and  drying 
to  all  the  dirt,  cinders,  and  sulphurous  gases  of  the  mill,  which  are  a 
fruitful  cause  of  decay  in  a  dried  coating  of  paint,  and  find  an  easier 
field  in  the  green  one.  The  mill-coated  work  is  not  allowed  time  to 
dry  before  being  loaded  for  transportation,  which  adds  its  quota  of 
dirt  and  cinders  to  the  sticky  paint. 

All  the  subsequent  machine  operations  are  accompanied  by  more 
or  less  lubrication  of  the  tool,  and  the  oil  used  for  this  purpose  is  the 
cheapest  to  be  had,  and  in  general  has  been  used  over  and  over  again ; 
is  dirty,  sour,  and  more  or  less  decomposed,  and  carries  enough  hydro- 
carbon to  evaporate  and  dry  down  as  a  dirty  surface  skin,  hard  to 
distinguish  from  the  coating  applied  at  the  mill.  The  sequence  is 
that  the  inspector  crowded  to  get  the  work  out  of  the  shop,  and  if  at 
all  careless  in  the  discharge  of  his  duty,  does  not  personally  see  that 
the  scales,  dirt,  and  machine-grease  are  properly  removed.  The 
painter,  anxious  to  show  a  great  day's  labor,  and  as  a  class  prone  to 
scrimping  everything  that  calls  for  any  manual  effort  other  than 
with  his  brush,  and  jealous  of  any  attempt  to  confine  him  to  a  pro- 


24  PAINTING  AT  THE  MILL. 

cedure  at  variance  with  what  he  thinks  is  a  special  function  of  his 
craft,  hastens  to  get  on  the  paint,  and  takes  more  credit  to  himself 
in  being  able  to  beat  the  inspector  than  to  do  a  meritorious  piece  of 
work. 

Rather  let  the  material  go  from  the  mill  or  forge  to  the  storeroom  or 
construction  shop,  protected  as  far  as  possible  from  any  unnecessary 
exposure  to  the  elements.  When  machined,  during  which  process 
the  greater  part  of  the  mill-scale  will  be  loosened  up  so  as  to  be  readily 
removed,  and  when  the  several  parts  are  assembled  in  their  relative 
positions  ready  to  be  riveted  up  for  their  permanent  places  in  the 
structure,  if  it  is  to  be  done  at  the  shop  instead  of  in  situ;  then  and 
there  is  the  place  for  the  inspector  to  determine  if  the  several  parts 
are  not  only  properly  machined,  but  also  properly  cleaned  from  the 
scale  that  has  not  been  removed  by  the  machining  and  handling. 
He  should  see  that  grease,  dirt,  and  any  remaining  scale,  tight  or  loose, 
is  removed  in  his  presence,  and  the  first  coat  of  the  paint  applied  in  a 
manner  to  meet  the  atmospheric  conditions  at  the  time,  and  use  a 
quality  of  paint  that  will  ensure  more  than  a  guess  at  the  future  pro- 
tective result. 

Nothing  can  then  serve  as  a  cloak  to  hide  the  inspector's  responsi- 
bility for  the  result.  One  inspector,  and  one  inspection  at  the  final 
stage,  is  better  than  a  number  of  inspectors  and  inspections  strung 
over  a  chain  of  operations  comprising  months  of  time  and  hundreds  of 
miles  between  the  links. 

Many  engineers  advocate  the  use  of  boiled  oil  alone  for  the  first  or 
priming  coat,  applied  either  at  the  rolling-mill  to  protect  the  metal 
during  its  transit  from  the  mill  to  the  construction  shop,  or  at  the  shop 
when  ready  to  ship  for  erection.  The  general  reason  as£  igned  for  this 
practice  is,  that  the  boiled  oil  "soaks  into  the  scale  and  dries  and  pre- 
vents further  tendency  towards  corrosion." 

This  theory  is  absolutely  without  proof,  from  any  standpoint. 
How  far  any  oil  or  liquid  can  soak  into  iron  or  steel  or  the  still 
harder  mill-scale  that  forms  on  these  metals,  these  Solons  do  not 
state.  The  use  of  such  oil  coatings  is,  in  general,  to  conceal  some 
slop-work  on  the  part  of  the  inspector,  or  constructor,  at  an  earlier 
stage  of  the  work  than  would  be  possible  later  on.  However  consist- 
ent and  beneficial  the  first  coating  of  oil  may  be  for  a  wood  or  masonry 
surface,  it  has  no  part  or  parcel  on  a  metallic  one,  when  applied  for 
the  correction  of  the  mill-scale  evil.  No  number  of  these  oil  or  even 
paint  coatings  will  soak  into  and  bond  these  scales  together,  or  to 


BOILED  LINSEED-OIL  COATINGS.  25 

the  metal  surface.  There  are  hundreds  of  records  of  the  painting 
of  important  railway  structures,  where  the  first  coat  of  boiled-oil 
method  was  used,  and,  in  the  great  majority  of  instances,  the  utter 
and  rapid  failure  of  the  coating,  and  the  extra  corrosion  of  the  struc- 
ture, could  be  directly  assigned  to  this  so-called  method  of  protection. 

The  weather-resisting  power  of  an  oil  coating  is  almost  nil  com- 
pared with  a  paint,  as  before  referred  to  in  Dr.  Dudley's  experiments 
(Chapter  I).  If  the  advocates  of  oil  coatings  are  so  sure  of  its  bene- 
fits as  against  a  paint,  why  not  make  all  the  coatings  of  oil  alone,  no 
matter  what  it  covers,  a  wire  or  an  anchor?  It  will  soak  as  far  into 
one  as  the  other.  A  paint  coating  can  be  applied  as  quickly  and  easily 
to  any  surface  as  an  oil  coat;  will  dry  as  quickly  and  as  hard,  and  is 
in  every  way  a  better  resistant  to  atmospheric  or  mechanical  injuries. 

A  foundation  coat  of  oil  is  a  direct  cause  of  the  blistering  and  peeling 
of  the  coatings  spread  over  it.  It  is  seldom  dried  enough  before  the 
other  paints  are  spread  over  it,  to  ensure  a  close  adherence  to  the  metal 
it  covers.  When  the  subsequent  coats  of  paint  are  spread,  the  solvents 
and  oils  in  them  soften  to  some  extent  the  underlying  coat  of  oil,  and 
a  moderate  heat  from  the  sun  causes  the  whole  coating  to  blister  or 
peel.  Too  much  oil  in  a  paint  coating,  particularly  if  the  surplus  oil 
is  in  or  near  the  foundation  coat,  whether  on  a  wooden  or  metallic 
surface,  will  generally  cause  peeling  regardless  of  the  pigment  used  in 
the  coatings. 


CHAPTER   III. 

IRON. 

Symbol,  FE.     Atomic  weight,  56.     Specific  gravity,  7.77. 

IRON  is  never  found  pure  in  nature.  Its  avidity  for  oxygen  is  so 
great  that  it  quickly  forms  lerrous  oxide,  FeO,  or  the  protoxide  of 
iron.  This  also  is  never  found  free,  and  is  difficult  to  obtain  chemi- 
cally pure,  its  affinity  for  oxygen  forming  the  sesquioxide — Fe2O3 — 
called  also  the  peroxide  (the  highest  form  of  oxide  for  any  metal) 
in  which  two  atoms  of  iron  and  three  of  oxygen  are  united,  or  70 
per  cent  of  iron  and  30  per  cent  of  oxygen. 

In  the  latter  form  it  is  commercially  known  as  iron  oxide  or  iron 
ore,  and  is  found  in  all  parts  of  the  world  in  all  stages  of  purity,  and 
in  combination  with  the  oxide  of  all  the  other  metals  in  all  propor- 
tions. The  color  of  the  protoxide  is  a  green  hue  changing  to  a  red- 
brown — that  of  the  peroxide  is  a  blood-red. 

An  intermediate  oxide — the  black  magnetic,  Fe3O4,  three  atoms 
of  iron  and  four  of  oxygen  =  72.4137  percent  of  iron  and  27.5863  per 
cent  of  oxygen — is  the  purest  oxide  of  iron. 

The  ferric  anhydride,  FeO3,  is  not  known  in  nature,  but  is  sup- 
posed to  be  formed  by  fusing  iron  or  its  oxide  with  nitre.  Its  co]or 
is  a  deep  crimson. 

Iron  at  a  temperature  of  230°  C.  (446°  F.)  combines  freely  with  the 
atmospheric  oxygen,  becoming  first  covered  with  an  extremely  thin 
film  of  magnetic  oxide,  Fe3O4,  of  a  light  yellow  color,  which  gradually 
passes  into  red,  blue,  and  gray  color.  At  a  white  heat,  iron  burns  in 
the  air  with  a  production  of  magnetic  oxide,  the  combustion  being 
sustained  for  some  time  by  directing  a  blast  of  air  upon  the  heated 
metal.  At  a  temperature  of  360°  C.  (680°  F.),  iron  decomposes  steam, 
forming  the  black  magnetic  oxide  of  iron,  Fe3O4  (the  Bower-Barff 
coating),  and  liberating  hydrogen. 

Crocus,  a  fine  powder  formed  when  iron-scrap,  borings,  or  ore  are 
placed  in  contact  with  malleable-  or  cast-iron  articles  in  a  closed  recep- 
tacle, and  all  brought  to  a  red  heat  for  the  purpose  of  annealing 
them,  is  anhydrous  iron  oxide,  Fe2O3,  of  a  dull  red-brown  color.  It 

26 


OXIDES  OF  IRON.  27 

is  no  better  when  used  for  a  pigment  than  any  natural  iron  ore,  other 
than  in  its  freedom  from  sulphur.  It  hydrates  on  exposure  to  the  air 
or  moisture  to  Fe2O3+H2O,  and  can  be  reduced  to  metallic  iron  the 
same  as  any  iron  ore. 

The  precipitate  formed  from  metallic  iron  when  corroded  under 
water  is  the  sesquioxide  or  peroxide  of  iron,  Fe2O3,  plus  three  parts 
or  24  per  cent  of  water,  and  is  red  rust,  Fe2O3+3H2O.  It  is  a 
dull  reddish-brown  color,  nearly  a  pure  oxide,  containing  only  such 
other  metallic  oxides  as  the  iron  contained  from  which  it  was  cor- 
roded. It  is  comparatively  free  from  sulphur,  more  so  than  the  best 
hematite  ore. 

Oxides  of  Iron. 

If  purity  of  an  iron-oxide  pigment  is  any  factor  to  prevent  corrosion, 
these  pure  oxides  ought  to  be  better  than  any  ircn-oxide  ores;  but 
they  are  not,  and  plainly  show  that  the  failure  of  all  iron  oxide- 
pigments  to  prevent  corrosion  on  a  ferric  body,  or  to  add  any  resist- 
ance to  the  decay  of  the  paint  coating,  lies  in  the  natural  inadequacy 
of  a  ferric  pigment  to  resist  its  own  inherent  weakness,  namely,  con- 
veying excessive  amounts  of  oxygen  with  a  tendency  to  excite  elec- 
trolytic action. 

Experiments  determine  that  bright  iron  placed  in  an  atmosphere 
of  dry  oxygen,  or  of  dry  carbonic  acid,  will  not  rust;  when  put  in  a 
damp  atmosphere  of  oxygen,  it  rusted  slightly;  in  a  damp  atmos- 
phere of  carbonic  acid,  a  small  quantity  of  white  carbonate  of  iron 
is  formed  on  the  surface  of  the  bright  metal,  but  no  rusting  takes 
place.  When,  however,  bright  iron  is  placed  in  a  damp  mixture  of 
the  two  gases — oxygen  and  carbonic  acid — it  is  rapidly  oxidized 
into  copious  excrescences  of  red  rust. 

In  the  opposite  direction,  to  prevent  rusting,  a  strong  solution  of 
carbonate  of  soda  preserved  needles  and  steel  instruments,  bright 
and  untarnished,  after  thirty  years  of  exposure,  and  would  probably 
do  so  forever 

Bright  steel  or  iron  objects  remain  untarnished  in  an  atmosphere 
of  dry  muriate  of  lime,  also  in  the  dry  carbonate  of  lime.  Iron  im- 
mersed in  lime-water,  caustic  potash,  and  caustic  soda  does  not  rust; 
though  the  lyes  absorb  carbonic  acid,  they  do  not  absorb  oxygen. 

The  solutions  of  chloride  of  soda,  kalium,  magnesium,  and  ammo- 
nium quicken  the  formation  of  rust  the  same  as  dilute  solutions  of 
acids,  if  free  oxygen  has  access.  Under  atmospheric  influences 


28 


OXIDES  OF  IRON. 


that  oxidize  zinc,  lead,  and  copper,  the  layer  of  the  oxide  formed  is 
measurably  thick  and  prevents  any  further  oxidation.  On  the  con- 
trary, iron-rust  once  formed  on  a  ferric  surface  never  ceases  its  action 
so  long  as  it  is  in  contact  with  it.  Rust  produces  rust. 

The  blush  of  oxide  that  appears  upon  the  surface  of  a  piece  of 
bright,  clean  iron,  such  as  is  left  from  the  action  of  the  sand-blast  or 
of  a  grindstone,  forming  after  a  few  hours  of  atmospheric  exposure 
and  can  be  wiped  off  by  the  hand;  or  the  piece  of  red  rust  fiom  the 
iron-scrap  heap;  or  the  scales  from  the  bottom  or  frame  of  an  iron 
ship;  one  and  all  are  the  peroxide  of  iron,  Fe2O3,  plus  three  parts  or 
24  per  cent  of  water.  When  calcined  to  drive  off  the  water,  they 


'^^i^ss^ 

tl^^sW^S^i^^. 


FIG.  4. — Rust  produced  on  a  clean  rolled-iron  plate  exposed  to  atmospheric 
influences  for  20  days.     (Andes.) 

become  precisely  the  same  ferric  oxide  contained  in  any  iron  ore,  and 
will  reduce  to  metallic  iron  or  grind  to  a  pigment  the  same  as  any 
iron  ore,  however  they  may  be  designated  or  juggled  with  trade- 
names. 

In  the  corrosion  of  iron  from  any  cause,  for  every  8  grains 
in  weight  gained  by  the  iron,  46  cubic  inches  of  hydrogen  weighing 
1  grain  are  set  free.  With  each  ounce  of  gain  in  the  weight  of  the 
iron,  2515.625  cubic  inches  of  hydrogen  (=1.4558  cubic  feet)  are 
evolved,  weighing  $•  ounce.  Every  pound  of  the  oxide  of  iron  re- 
quires the  evaporation  and  dissociation  of  .29628  of  a  pound  of  water, 
representing  the  energy  of  about  1  pound  of  coal. 


OXIDES  OF  IRON. 


29 


The  magnetic  oxide  of  iron  is  the  richest  of  the  iron  ores  in  metallic 
iron  =72.414  per  cent.  It  is  non-corrosive,  and,  in  the  form  of  black 
titaniferous  sand,  found  on  the  seacoast  in  many  parts  of  the  world, 
exposed  to  sea-water  and  other  sources  of  oxidation  and  friction,  has 
remained  unchanged  for  thousands  of  years.  Its  use  for  a  pigment 
is  not  satisfactory,  on  account  of  its  black  color  and  the  difficulty 
of  grinding  it. 

Specular  iron  ore  is  also  but  little  affected  by  oxidation,  and  is  a 
nearer  approach  to  a  definite  compound  of  iron  and  carbon  than  any 
other  known  ferric  substance:  iron,  94.85  per  cent;  carbon,  combined 


FIG.  5. — Rusting  of  a  clean  rolled-iron  plate  from  a  single  application  of  water 
and  left  to  dry.     (Andes.) 

and  graphitic,  3.50  per  cent;  silica,  manganese,  sulphur,  and  phos- 
phorus, 1.65  per  cent.  It  is  an  anhydrous  ferric  oxide,  found  in 
Nova  Scotia,  in  the  Isle  of  Sicily,  and  other  parts  of  Europe, 
where  mines  of  it  have  been  worked  for  3000  years.  Its  black  color 
and  hardness  prevent  its  use  as  a  pigment,  though  its  resistance  to 
corrosion  is  almost  equal  to  that  of  the  Bower-Barff  surface. 

The  clay-iron  ores  from  the  coal  measures,  the  spathic,  bog,  and 
many  other  iron  ores,  contain  a  very  small  amount  of  iron,  and  so 
large  an  amount  of  silica  and  other  mineral  substances  that  they  are 
too  refractory  for  smelting.  They  are  not  used  for  pigments  for  the 
same  reasons  that  attend  the  magnetic  and  specular  ores. 


30  HEMATITE  ORES. 


Hematite  Ores. 

The  red  and  brown  hematite-iron  ores,  composed  of  the  sesqui- 
oxide  of  iron — 70  per  cent  metallic  iron  and  30  per  cent  oxygen,  plus 
water,  plus  variable  percentages  of  mineral  substances,  plus  carbonic, 
sulphuric,  and  phosphoric  acids  (see  following  analyses) — are  the 
principal  metallurgical  iron  ores,  also  those  used  for  the  production 
of  pigments  under  the  name  of  iron  oxides,  Fe203.  This  chemical 
symbol,  name,  and  product  is  subject  to  more  commercial  jugglery 
to  meet  trade  requirements  than  any  other  pigment  in  use.  It  is 
made  to  cover  all  sorts  of  combinations  diverse  in  composition  and 
character,  supplemented  still  further  by  quantities  of  so-called  inert 
bodies,  more  unstable  than  those  in  the  ore  with  which  they  have 
been  brought  into  forced  relation. 

These  hydrated  ores  when  calcined  to  expel  the  moisture — sul- 
phuric, phosphoric,  carbonic,  and  other  erroneously  supposed  easily 
evaporated  acids — become  the  anhydrous  or  supposed  neutral,  Fe2O3, 
plus  about  2  per  cent  of  water  in  a  combined  form,  plus  the  acid 
elements  that  frequently  amount  to  2  per  cent.  Only  30  to  50  per 
cent  of  the  sulphuric  and  phosphoric  acids  are  dispersed  in  the  com- 
paratively low  heat  of  the  roasting  process,  and  are  not  wholly  con- 
sumed in  the  high  heat  of  the  blast-furnace,  as  manufacturers  of 
metallic  iron  find  to  their  annoyance. 

The  lime,  magnesia,  alumina,  silica,  manganese,  and  other  oxides, 
whether  in  a  combined  state  in  the  ore,  or  as  added  free  substances  at 
the  time  of  roasting  by  calcination,  become  caustic  and  hygroscopic, 
and  when  ground  to  a  pigment  form,  absorb  moisture  from  the  atmos- 
phere, slack,  changing  their  character  again  more  or  less  to  a  floccu- 
lent  or  a  powdered  state.  They  do  not  bond  in  the  slightest  degree 
to  the  oxide  of  iron  or  base,  are  no  more  connected  with  it  or  to  each 
other — except  in  a  haphazard  arrangement  of  their  disrupted,  sepa- 
rate natures — than  the  same  substances  would  be  if  collected  from  a 
sand-bank. 

No  mechanical  process  connected  with  their  incorporation  into 
a  pigment  or  paint  can  arrange  them  in  sequence,  or  in  any  order 
where  either  substance  can  be  supposed  to  protect  its  neighbor  or 
even  itself  from  any  disturbing  cause.  Their  excited,  unstable 
condition  and  close  association  in  a  finely  powdered  form  in  the 
paint,  render  them  only  the  more  susceptible  to  catalytic  action 
among  the  several  substances  of  the  pigment.  This  action  soon  de- 


IRON  ORES,  QUALITIES  OF.  31 

stroys  the  weakest  of  them  by  electrolysis,  set  in  action  by  their 
association  as  positive  and  negative  electrical  elements,  or  by  the 
catalytic  power  of  nearly  all  finely  powdered  substances  to  condense 
moisture  and  gases  from  the  atmosphere,  which  the  porous  nature  of 
the  paint  coating  readily  absorbs.  If  sulphur  is  present  in  either 
the  pigment  or  vehicle  in  any  recognizable  quantity  (as  it  nearly 
always  is),  it  furnishes  an  additional  excitant  for  the  electrolytic 
action.  This  electrolytic  action  is  further  intensified  by  the  unequal 
composition  of  all  iron  ores,  whether  roasted  or  not.  The  process  of 
roasting — always  an  uncertain  one — does  not  affect  the  ore  equally. 
Lumps  improperly  roasted,  or  from  their  composition  affected  dif- 
ferently by  the  process,  are  difficult  to  detect  in  the  hasty  and  gener- 
ally poor  assorting  or  picking-over  the  ore  receives  before  pulveriz- 
ing. The  same  uncertainty  in  the  composition  and  assorting  attends 
the  unroasted  ores. 

In  the  pulverizing  process  there  are  many  larger  and  harder 
particles  of  the  ore  that  would  not  pass  a  No.  50  mesh  sieve,  if 
the  pigment  were  bolted  (as  it  seldom  is),  and  would  much  less  pass 
a  100  mesh,  to  which  size  all  pigments  should  be  reduced. 

The  finer  the  pigment  the  more  thoroughly  will  it  incorporate 
with  the  vehicle  and  protect  itself  and  the  surface  covered.  The 
destruction  of  any  particle  of  the  pigment  will  not  render  the  coating 
so  porous  as  when  a  larger  atom  is  removed  to  permit  access  for  the 
atmospheric  moisture  and  gases.  These  lumps  act  as  centres  to 
determine  the  corrosive  action,  and  in  a  measure  explain  the  erratic 
action  of  all  iron-oxide  coatings.  In  nearly  all  rust-spots,  one  or  more 
of  these  hard  particles  will  be  found,  and  particularly  so  wherever 
pitting  has  commenced. 

The  brown  hematite  ores  are  claimed  to  be  practically  free  from 
sulphur,  therefore  the  best  for  a  pigment;  but  the  best  brands  of 
this  variety  of  ore  prepared  by  any  one  of  the  many  manufacturers  of 
unroasted  iron-oxide  pigments  have  not  proved  to  be  in  the  slightest 
degree  any  more  reliable  in  composition,  or  any  better  protection 
against  corrosion — whether  used  as  a  straight  paint  or  mixed  with 
adulterants — than  those  prepared  from  the  red  hematites.  (See 
following  analyses  of  both  pigments  as  used  in  commercial  paints.) 

The  dirty  purplish-brown  or  lifeless  color  of  the  brown  hematites, 
even  when  freshly  applied  and  aided  by  the  gloss  of  oil,  is  not  agreea- 
ble to  the  eye.  Their  ability  to  carry  a  large  amount  of  uncombined 
substances,  as  inert  pigments  which  add  no  quality  to  the  paint  as  a 


32 


IRON  ORES,  ANALYSES. 


protective  agent,  and  the  low  cost  of  the  whole  line  of  iron-oxide 
pigments,  are  the  great  inducements  for  their  production  and  use 
for  ferric  coatings. 

ANALYSES  OF  IRON  ORES. 

BY  VARIOUS  ANALYSTS. 
(Specific  gravity  from  5.33  to  4.85.) 


Brown  Hematite  (Limonite), 
24  Different  Ores  (Hydrated). 

Red  Hematite,  8  Different 
Ores  (Anhydrous). 

Percentages. 

Av'ges. 

Percentages. 

Av'ges. 

Ferric             oxide  from 
Ferrous 
Manganous                   ' 
Alumina 
Lime 
Magnesia 
Silica 
Carbonic  acid 
Phosphoric  " 
Sulphuric     " 
Iron  pyrites  ^              " 
Water  combined  and  h 
groscopic  

y- 

90.05  to  32.76 
traces   "    10.54 
3.06    "      0.05 
27.95          0.05 
0.06        27.72 
0.17         10.21 
63.52          0.79 
0.16         18.45 
0.06           3.17 
traces          0.28 
0.30 

18.60    "      6.60 

59.54 
1.22 
0.87 
4.48 
4.20 
1.30 
13.90 
3.83 
0.63 
0.03 
0.03 

10.25 

98.71   to  66.55 
traces   "      1.13 
1.13    "     0.10 
2.79   "     0.06 
9.40    "     0.37 
1.39   "      0.08 
8.90   "      1.00 
5.73    "      0.78 
1.02    "   traces 
1.31    "        " 
traces 

2.12    "       " 

89.13 
00.16 
0.31 
0.82 
1.97 
0.42 
5.77 
1.35 

traces 
ii 

ii 
ii 

Percentages  of  metallic  iron  63.04  to  24.09     42.45 
11  samples  averaged  52.65  per  cent  of  iron. 
13        "              "       33.81     "     "      "      " 

66.10  to  47.47 

Only    one     samp 
below  66  per 
iron. 

62.37 

le    was 
Bent  of 

There  is  a  wide  difference  among  these  comparatively  few  and 
better  quality  ores,  selected  from  many  hundreds  of  ore-beds,  on 
account  of  their  purity  and  high  percentage  of  metallic  iron. 

Many  other  mines  furnish  ores  that  are  worked  for  the  other 
metallic  and  chemical  substances  they  contain,  as  nearly  all  the  other 
metals  are  found  associated  with  iron.  All  iron  mines  are  noted 
for  the  variable  quality  of  the  ore  taken  from  the  same  or  from  the 
adjoining  bed,  or  from  different  parts  of  the  same  vein  in  each  mine. 
The  hematites  are  not  exempt  from  this  feature,  whether  used  metal- 
lurgically  or  for  pigments. 

Though  an  analysis  may  show  an  iron  ore  to  be  good  for  metallur- 
gical purposes  it  does  not  follow  that  such  an  ore  is  suitable  for  a  pig- 
ment, however  much  the  hematites  may  be  desired  as  such,  on  account 
of  their  supposed  freedom  from  sulphur  or  ease  in  grinding  them 
tinroasted. 


IRON-OXIDE  PIGMENTS.  33 

Ores  containing  40  to  60  per  cent  of  the  sesquioxide  of  iron  and 
30  to  50  per  cent  of  silica  have  not  proved  to  be  any  better  protection 
against  corrosion  than  those  containing  80  to  95  per  cent  of  the  ses- 
quioxide. This  will  be  apparent  by  reference  to  the  composition  of 
the  iron-oxide  pigments  given  in  the  tests  of  commercial  paints, 
Chapter  XXX. 

Iron-oxide  Pigments. 

The  red  hematites  furnish  a  brighter-colored  oxide  than  the  brown 
hematites,  whether  roasted  or  not.  The  small  amount  of  sulphur 
in  the  red  ore  develops  in  the  process  of  roasting  the  dull-red  color 
into  a  brighter  red,  simulating  the  Venetian  and  Indian  reds  so  desira- 
ble to  produce,  but  not  always  possible  to  get  without  doctoring  the 
furnace  product  subsequently  with  substances  more  complex  and  un- 
stable than  the  iron  oxide  itself.  (See  inert  pigments,  Chapter  XVIII.) 
The  roasting  process  is  a  sensitive  one.  A  few  degrees  of  higher 
or  lower  temperature,  or  a  little  difference  in  the  period  of  exposing 
the  ore  to  it,  or  in  the  manner  of  cooling  down  the  furnace,  cause  a 
great  range  in  the  color.  The  more  sulphur  in  the  ore  the  brighter 
the  color. 

There  are  from  10  to  20  per  cent  of  moisture  and  carbonic  acid 
in  all  iron  ores  as  they  come  from  the  mines.  If  these  are  not  driven 
off  by  roasting,  they  will  not  be  dissipated  in  the  pulverizing,  and 
will  be  carried  by  the  pigment  into  the  mixed  paint  to  its  detriment. 
The  use  of  an  uncalcined  iron-ore  pigment  is  a  long  step  toward  an 
early  corrosion  of  the  ferric  body  over  which  it  is  spread. 

The  following  analysis  of  an  iron-oxide  pigment  made  from  a 
special  red  hematite  roasted  ore,  one  of  the  oldest  and  best  known  of 
this  class  of  pigments,  and  the  use  of  which  as  a  special  brand  is 
probably  greater  than  all  of  the  other  brands  of  iron-oxide  pigments 
in  the  world,  is  of  interest  for  comparison  with  an  unroasted  ore  pig- 
ment: 

MANUFACTURERS'  ANALYSIS. 

Peroxide  of  iron 52 . 11  per  cent. 

(Equivalent  in  metallic  iron,  36.477 
per  cent.) 

Silica  combined , .  .  .  .46.03   "        " 

Lime 0.23  " 

Moisture 1 .59  "        " 

Loss 0.04  "        " 

100.00  " 


34  IRON -OX  IDE  PIGMENTS. 

Certainly,  this  is  a  pigment  that  should  show  a  good  result  on 
either  wood  or  iron  surfaces,  if  there  is  any  protective  value  in  iron 
oxide.  However,  notwithstanding  its  almost  uncontested  use  for 
over  thirty  years,  on  account  of  its  low  cost,  agreeable  color,  and 
much  lauded  protective  virtues,  it  proved  so  unsatisfactory  for  both 
wood  and  iron  coatings  that  various  railway  companies — the  largest 
consumers  of  paints — have  reduced  the  50  per  cent  of  this  peroxide 
of  iron  admissible  in  their  mixed-color  paints  to  25  per  cent.  But 
this  change  has  not  resulted  in  any  marked  improvement  in  the 
protective  qualities  of  the  paint  when  applied  to  ferric  bodies,  nor 
are  better  results  apparent  upon  wooden  surfaces. 

The  following  analysis  is  of  a  brown  hematite  unroasted  iron  ore. 
With  a  number  of  other  brands  of  similar  composition,  it  has  been 
largely  used  by  construction  and  railway  engineers  upon  hundreds 
of  the  most  important  ferric  structures  in  the  country,  whose  serious 
corrosion,  after  but  a  short  period  of  exposure,  led  to  a  special  exam- 
ination and  report  on  their  condition  to  the  engineering  firms  responsi- 
ble for  their  erection  and  condition : 

Peroxide  of  iron 93 . 04  per  cent. 

(Equivalent  in  metallic   iron, 
65.128  percent.) 

Silica  combined 3.28     "  " 

Alumina  combined 2 . 385  "  " 

Lime  and  magnesia 0. 66    "  " 

Organic  and  volatile.  .  •. 0.42     "  " 

Sulphuric  acid 0 . 03     "  " 

Moisture  and  loss.  .  0.185"  " 


100.00     "       " 

This  is  a  high-grade  metallic  iron  ore  comparatively  free  from  sul- 
phur, and  whose  merit  as  an  anti-corrosive  pigment  was  greatly  com- 
mended (by  the  manufacturers)  for  a  straight  paint  free  from  the 
usual  class  of  inert  adulterants.  But  its  protective  results  as  detailed 
in  the  said  report  were  not  better  than  the  other  adulterated  oxide 
pigments,  or  the  other  coatings  of  mixed  or  unknown  composition. 

The  following  is  an  analysis  of  an  iron-oxide  pigment  that  is 
reported  to  have  given  very  good  results,  being  among  the  best  of 
that  class  of  compounded  iron-oxide  paints :  * 

*  Messrs.  Hunt  &  Clapp,  chemists  and  bridge  inspectors,  Philadelphia  lind 
Pittsburg, 


IRON-OXIDE  PIGMENTS.  35 

Iron  oxide.  .  .   26.72  per  cent  \  =  iof  IS'™P*  cent 

(      of  metallic  iron. 

Carbonate  of  lime 30.19  "  " 

Sulphate  of  lime 14.05  "  " 

Clay  and  silica 19.90  "  '" 

Alumina 8.18  "  " 

Magnesia   0.52  "  " 

Water  and  organic  matter  0.44  "  " 

100.00   "      " 

Additional  examples  of  iron-oxide  paints  and  their  erratic  action 
— both  mixed  and  straight  pigments — will  be  found  in  the  article  on 
paint  tests,  Chapter  XXX. 

It  is  claimed  that  iron-oxide  pigments,  being  the  peroxide  of 
iron,  are  incapable  of  further  oxidation,  and  when  ground  with  the 
vehicle  are  indestructible,  and  their  capacity  to  condense  atmos- 
pheric moisture  and  gases  ceases.  This  is  true  as  long  as  the  thin 
film  of  the  dried  vehicle — only  ^  to  yj^  inch  in  thickness — 
remains  in  place  on  the  external  surface  of  the  pigment  atom,  and 
no  longer.  The  same  causes  that  remove  this  film  will  affect  the 
other  part  of  the  vehicle,  in  which  the  pigment  atoms  are  im- 
bedded. The  vehicle,  passive  of  itself  to  condense  atmospheric 
moisture  or  gases,  is  porous  and  absorbent;  and  passes  them  on  to 
the  point  where  their  decomposing  action  can  take  effect,  if  not  on 
the  iron-oxide  atom,  then  upon  the  less  resisting  mineral  substances 
associated  with  it  as  a  pigment. 

With  the  possible  exception  of  silica  and  barytes,  all  of  the 
so-called  inert  substances,  usually  mixed  with  iron-oxide  pigments, 
are  porous  and  absorbent  of  the  vehicle  and  gases  that  reach 
them.  The  protection  that  these  inert  substances  receive  from 
the  oil  is  no  greater  than  the  oil  affords  the  iron-oxide  atom,  if  not 
less,  owing  to  the  unreliable  character  of  their  composition  naturally. 
If  they  have  been  mixed  with  the  iron  ore  during  the  process  of 
roasting,  they  are  rendered  more  unstable,  and  readily  pass  to  a 
lower  plane  of  resistance,  as  mentioned  before. 

It  may  be  questioned  whether  iron  oxide  is  incapable  of  con- 
densing moisture  or  gases.  It  induces  and  promotes  oxidation  in 
all  organic  bodies  with  which  it  is  brought  into  contact,  and  is  used 
in  the  process  of  boiling  oil  to  increase  the  catalytic  power  of  all 
siccative  oils  to  absorb  oxygen  from  the  air.  Its  use  with  raw  linseed 


36  IRON-OXIDE  PIGMENTS. 

and  other  oils  is  to  absorb  the  glyceride  element  that,  unabsorbed 
or  unchanged,  in  all  fatty  oils  delays  the  drying  process,  condensing 
the  atmospheric  moisture  and  gases  that  act  below  the  external 
film  of  the  drying  oil,  thus  laying  the  foundation  for  a  blister  with 
subsequent  corrosion  of  the  coated  surface. 

The  power  of  iron  oxide  to  absorb  the  glyceride  is  about  two- 
thirds  that  of  red  lead.  If  the  iron-oxide  atom  is  insensible  to  the 
presence  of  sulphur  that  may  be  presented  to  it  in  any  form,  the 
other  associated  mineral  substances  and  vehicle  are  not,  and  a 
very  small  percentage  of  any  acid  will  set  in  motion  the  electrolytic 
action  so  fatal  to  ferric  substances. 

As  a  class,  the  inert  pigments  are  electro-positive  to  the  iron- 
oxide  atom,  and  are  the  first  to  be  affected  by  any  electrolytic  action 
inaugurated  by  their  presence  in  the  paint. 

The  iron-oxide  atoms  are  electro-negative  to  the  ferric  surface 
over  which  they  are  spread. 

In  iron-oxide  and  zinc-oxide  mixtures,  the  iron  atom  is  electro- 
negative to  the  zinc  atoms,  which  are  quickly  destroyed.  If  any  copper 
or  copper  oxide  is  present  in  an  iron-oxide  pigment,  the  iron  oxide 
is  electro-positive  to  the  copper  and  is  destroyed. 

Mallet's  experiments  determined  that  copper  and  zinc  in  any 
form;  added  to,  or  in  contact  with  iron  in  any  form,  increased  the 
corrosion  of  a  covered  iron  surface  60  per  cent  in  a  given  time ;  copper, 
without  the  zinc  element,  40  per  cent. 

The  irregularity  of  the  distribution  of  the  atoms  in  a  compound 
iron-oxide  coating — their  difference  in  size  and  character — deter- 
mine the  points  of  corrosion,  which  once  established  end  only  with 
the  complete  failure  of  the  coating. 

From  five  to  ten  per  cent  of  the  sulphate  of  lime  (CaOSO3)  is 
generally  found  in  iron-oxide  paints  or  pigments.  It  is  usually  speci- 
fied by  the  consumer  that  it  shall  be  fully  hydrated,  or  that  it  shall 
contain  not  more  than  one  part  of  water.  The  effect  of  the  moisture 
is  to  aid  any  sulphur  element  present  to  commence  promptly  its 
work  of  disintegrating  the  coating.  From  its  great  covering  power, 
the  ease  of  grinding  and  mixing  it  with  the  iron  oxide,  and  its  cheap- 
ness, one  third  of  the  weight  of  the  pigment  is  frequently  composed 
of  this  substance,  particularly  in  the  tint  colors.  The  greater  the 
amount  of  this  sulphate  of  lime,  the  sooner  the  destruction  of  the 
coating. 

The  copperas  oxides  of  iron  stand  remarkably  well  upon  wooden 


IRON-OXIDE  PIGMENTS.  37 

surfaces.  The  brown  oxides  stand  the  best  upon  ferric  bodies.  The 
Venetian  red  oxide,  from  the  old  iron-oxide  mines,  had  a  peculiar 
preservative  action  on  the  surface  of  wood.  Two  or  three  coats 
from  the  pure  materials  have  outlasted  the  record  of  their  appli- 
cation and  the  lives  of  the  painters  that  spread  them.  These  oxides 
and  white  lead  form  a  hard  mastic  covering,  and  unless  spread  over 
unseasoned  or  wet  wooden  surfaces,  are  not  liable  to  blister  or  peel. 

Many  of  the  irreconcilable  discrepancies  in  the  use  of  iron-oxide 
paints  can  be  attributed  to  the  careless  method  of  preparing  them. 
In  general  practice,  it  is  never  ground  with  the  oil,  and  but  seldom 
machine-mixed.  The  dry  pigment  in  the  ratio  of  six  to  seven  pounds 
and  about  the  same  weight  of  oil  (or  three-fourths  of  a  gallon)  are 
placed  together  in  a  tub,  and  after  a  few  hours  of  soaking  are  simply 
stirred  up  and  spread.  If  any  large  quantity  of  paint  is  so  pre- 
pared, it  is  almost  impossible  to  secure  thorough  incorporation  of 
the  pigment  and  the  oil,  owing  to  the  different  specific  gravities  of 
the  several  substances  composing  the  pigment,  which  vary  from 
2.2  to  4.9.  This  manner  of  mixing  is  strongly  recommended  by 
the  iron-oxide  trade  to  secure  its  use,  at  the  expense  of  the  life  and 
effectiveness  of  their  product,  which  many  times  might  be  more 
creditable  were  better  care  taken  to  render  it  deserving. 

The  longer  that  iron-oxide  paints  are  ground  in  the  full  quantity 
of  oil  they  require  to  form  a  paint,  the  more  lasting  they  will  be,  and 
this  effect  is  equally  apparent  in  all  pigments. 

The  unsatisfactory  results  due  to  careless  mixing  are  aggravated 
by  the  use  of  large  flat  brushes  that  act  as  mops  to  carry  or  slap 
on  a  large  quantity  of  paint,  inadequately,  in  this  way,  brushed  out. 
Such  brushes  carry  air  into  the  coating,  rendering  it  more  porous 
in  drying  than  it  otherwise  would  be  were  heavy,  long-bristle,  round 
brushes  employed.  The  same  objections  exist  where  the  coating 
is  applied  by  the  air-brush  or  spray  apparatus,  only  in  a  more  marked 
degree.  See  Chapter  XXXI. 

There  are  many  tests  for  the  adulteration  in  iron-oxide  pigments 
or  paints  of  too  extended  detail  to  be  entered  into  here.  A  ready 
test  for  the  soluble  sulphate  of  iron  in  an  iron  oxide  is  to  warm  a 
little  with  pure  water  and  filter  through  blotting  paper.  Add  to  the 
clear  solution  a  few  drops  of  hydrochloric  acid  and  a  little  of  the 
chloride  of  barium  (both  obtainable  at  any  drug  store).  If  a  white 
sediment  forms  in  the  solution,  the  sample  of  iron  oxide  should  be 
rejected. 


38  IRON-OXIDE  PIGMENTS. 

There  are  many  recorded  instances  of  the  excellent  results  attend- 
ing the  use  of  iron-oxide  pigments.  Berzelius  (1838)  mentions  that 
on  houses  in  Sweden,  painted  with  iron  oxide  three  hundred  years 
ago,  the  coating  was  still  in  fair  condition,  and  the  wood-work  well 
preserved.  The  wooden  houses  and  workshops  in  many  parts  of 
the  United  States  bear  testimony  equally  in  favor  of  this  class  of 
paints,  in  the  general  good  condition  of  the  paint  and  structure  after 
exposures,  without  repainting,  of  fifty  to  eighty  years.  But  in  every 
case  the  cause  of  these  excellent  and  exceptional  results  was  in  the 
use  of  better  materials  and  better  methods  of  application  than  is  the 
present-day  practice. 

Paint-trade  literature  frequently  cites  that  the  tin  roof  of  Independ- 
ence Hall  in  Philadelphia  has  been  protected  for  the  past  one  hundred 


FIG.  6. — Corrosion  of  the  present-day  make  of  tin  plate  after  storage  in  a  dry 
cellar  for  ten  years.     (Andes.) 

and  thirty  years  with  an  iron-oxide  paint,  giving  this  as  an  unanswera- 
ble argument  for  the  protective  character  of  these  pigments  applied 
to  metal  surfaces.  The  facts  in  this  case  show  that  the  plates  with 
which  this  particular  roof  was  laid,  as  well  as  many  others  at  that 
period,  were  double-coated  with  pure  block  tin,  free  from  lead,  zinc, 
or  antimony,  more  scrupulous  care  being  taken  in  every  part  of  its 
manufacture  to  secure  a  reliable  product,  than  is  now  practised  by 
even  the  best  of  the  present-day  tin-plate  manufacturers,  whose 
products  almost  universally  fail  by  the  corrosion  of  the  iron  plate 


OF  THE 

UNIVERSITY 

OF 


CORROSION  OF  TIN  ROOFS  39 

on  which  the  tin  is  coated.  This  internal  corrosion  casts  off  the  tin, 
and  no  amount  or  kind  of  paint  spread  upon  an  inferior  quality  of 
tin-roofing  metal  can  prevent  this  internal  corrosion,  though  it  may 
conceal  its  presence  and  progress,  and  possibly  fill  up  some  small  holes 
in  the  early  stages  of  the  decay. 

There  are  scores  of  tin  roofs  covering  important  buildings  in  the 
Canadian  Provinces  that  have  been  laid  for  nearly  a  century,  as  bright 
and  uncorroded  now  as  when  first  laid,  never  having  had  a  coat  of 
paint  to  protect  them. 

Pure  block  tin  is  unaffected  by  atmospheric  conditions,  almost 
as  much  so  as  copper.  It  was  only  when  poorly  cleaned  plates, 
poor  tin  for  the  coating,  acid  flux  instead  of  resin  for  soldering,  and 
careless  methods  of  laying  the  roof  generally,  came  into  vogue,  that 
we  began  to  hear  of  the  virtues  and  need  of  an  iron-oxide  paint  to 
prevent  the  corrosion  of  a  tin  roof.  Granted  that  a  good  quality 
of  tin  roofing  is  none  the  worse  for  a  coating  of  paint  applied  a 
year  or  two  after  the  roofing  is  laid,  yet  it  is  quite  as  essential 
for  the  future  life  of  the  roof  that  the  paint  should  be  also  of 
good  quality. 

The  original  mines  from  which  the  iron-oxide  pigments  known  as 
Indian  and  Venetian  reds  were  taken  have  long  been  exhausted. 
These  old  mine  pigments  required  no  roasting  or  doctoring  to  develop 
their  color,  or  to  correct  any  acid  elements  in  them.  The  reputa- 
tion of  these  pioneer  oxide  pigments,  like  that  of  the  "Old  Dutch 
Process"  white  lead,  has  been  assumed  to  reach  and  cover  the  advent 
of  scores  of  substances  bearing  little  resemblance  to  their  progenitors, 
except  in  name,  and  even  this  is  not  exempt  from  the  greed  of  some 
modern  paint-compounders,  as  the  many  prefixes  and  trade-marks 
bear  witness. 

Fig.  7  shows  the  protective  character  of  an  iron-oxide  paint 
applied  to  a  railway  viaduct  not  properly  cleaned  from  mill-scale 
before  painting,  and  when  painted  was  exposed  to  combustion  gases, 
cinders,  dust,  and  moisture. 

Prepared  iron-oxide  paints  are  often  brightened  by  the  use  of 
aniline  colors,  but  are  not  durable.  Burning  a  sample  of  such  paints 
over  an  alcohol  lamp  will  destroy  the  aniline,  and  leave  the  iron 
oxide  its  natural  color,  exposing  the  cheat.  The  tendency  of  all  iron- 
oxide  paints  is  to  darken  with  age,  due  to  the  natural  darkening  of 
the  oil  vehicle  by  age,  rather  than  by  change  in  the  pigment. 
While  nearly  all  of  the  iron-oxide  paints  are  adulterated,  barytes, 


40          COPPERAS  (SULPHATE  OF  IRON,  GREEN    VITRIOL). 

chalk,  sand,  silica,  and  all  added  substances  lessen  the  covering 
power.  The  clays  also  absorb  water  and  hasten  the  decay  of 
the  paint. 


FIG.  7- 


Copperas  Oxide. 

The  chemical  composition  of  copperas  is  Fe.SO4.7H20  =  one  part 
of  iron  plus  one  part  sulphuric  acid,  plus  seven  parts  of  water. 

Copperas,  the  waste  product  of  many  manufacturing  processes, 
is  largely  used  to  produce  an  oxide-of-iron  pigment  by  roasting  the 
crystals.  Six  parts  of  the  water  are  driven  off  by  a  heat  of  114°  F., 
but  one  atom  is  still  retained  at  280°  F.  At  a  red  heat  it  decom- 
poses, giving  off  one  part  of  sulphurous  oxide,  leaving  a  basic  ferric 
sulphate,  Fe2O33SO3;  and,  more  strongly  heated,  it  leaves  a  pure  ferric 
oxide  known  as  Colcothar  vitriol. 

As  usually  roasted  for  an  iron-oxide  pigment,  from  three  to  five 
pounds  of  terra  alba,  lime,  or  chalk,  to  one  of  the  ore,  are  put  in  the 
roasting-furnace,  heated  to  a  high  heat  to  expel  the  sulphur,  which 
is  supposed  to  combine  with  the  lime,  forming  a  synthetical  sulphate 
of  lime  (gypsum).  This  combination  is  the  same  as  in  the  roasting 
of  iron  ore  with  chalk  or  lime  to  remove  the  sulphur,  and  will  be 


IRON-OXIDE  PIGMENTS,  OCHRE.  41 

found  in  detail  in  the  list  of  inert  pigments  under  "Gypsum."  The 
process  is  a  sensitive  one,  the  color  of  the  product  being  the  bright- 
red  color  pigments, — Venetian  and  Indian  reds.  Both  colors  are 
due  to  the  degree  of  heat  employed,  the  length  of  exposure  to  this 
heat,  the  manipulation,  manner  and  time  taken  to  cool  the  mass, 
etc. 

All  of  the  sulphur  is  not  dissipated  by  the  heat  nor  absorbed  by 
the  lime  in  its  change  from  a  carbonate  to  a  sulphate.  The  lime 
changed  to  gypsum  or  left  free,  being  in  great  excess  of  the  amount 
that  is  allowable  in  any  pigment,  is  removed  to  some  extent  by  sift- 
ing, or  other  means,  before  grinding  the  furnace  product. 

Copperas  oxide  requires  great  care  in  its  use,  either  by  itself  or 
mixed  with  the  dead-color  iron  oxides  or  other  pigments  to  bring  up 
their  color,  as  the  sulphur  goes  into  the  paint  with  the  usual  results. 
No  amount  of  free  adulterants  or  inert  substances  have  any  material 
effect  in  neutralizing  it. 

Copperas  ferric  salt  (a  protosulphate  of  iron),  Coquimbite,  is 
found  native  as  a  hydrate,  containing  nine  atoms  of  water,  Fe2O33SO3 
+  9H2O.  It  occurs  in  layers  several  feet  thick  in  fine-grained  six- 
sided  pyramid  crystals.  Its  preparation  for  a  pigment  is  similar  to 
that  described  above,  and  the  resulting  disintegrating  effect  in  the 
paint  is  not  measurably  different. 

Yellow  Ochre. 

Ochre  is  a  hydrated  oxide  of  iron  of  a  strong  yellow  or  brown- 
yellow  color,  generally  containing  less  than  40  per  cent  of  iron  oxide. 
The  ochres  are  among  the  oldest  of  pigments.  Samples  have  been 
obtained  from  Pompeii  in  all  stages  of  preparation  from  the  ore  to 
the  mixed  paint.  They  were  used  in  Greece  in  the  time  of  Pliny, 
and  in  Old  Egypt.  They  are  the  most  stable  of  the  yellow  colors, 
and  are  the  principal  pigment  in  the  present  freight-car  colors. 

Ochres  are  clays  tinted  with  the  oxide  of  iron  and  manganese, 
and  hygroscopic  in  character,  carrying  from  five  to  fifteen  per  cent 
of  water.  Dried  artificially  to  expel  the  water,  they  change  color 
to  pink  or  red  the  same  as  all  other  iron-oxide  substances. 

Their  yellow  color  is  chiefly  due  to  the  iron  oxide,  and  the  more 
of  this  they  contain  the  darker  the  color.  The  brown  color  is  due 
to  the  manganese  oxide.  All  ochres  contain  some  amount  of  this 
oxide.  The  darker  colors  (unroasted)  contain  the  most  manganese, 
and  are  good  driers  for  use  with  linseed-oil. 


42  IRON-OXIDE  PIGMENTS,  OCHRE. 

The  covering  power  of  the  ochres  depends  upon  the  amount  of 
lime  or  chalk  in  them,  which  reduces  the  coloring  power  by  rendering 
them  translucent.  They  require  from  sixty  to  eighty  per  cent  of 
oil  to  form  a  paste,  and  the  added  quantity  of  oil  to  make  them  spread 
makes  them  slow  driers.  They  blacken  a  little  in  time  exposed  to 
sunlight,  but  the  change  in  tone  is  evidently  more  from  the  darkening 
of  the  oil  than  from  a  change  in  the  pigment. 

The  best  brands  of  ochre  are  the  French : 

Composed  of  clay 69.5  to  73.8  per  cent. 

Oxide  of  iron  and  manganese 23.5  "  25.6    "       " 

Water 7.0  "     9.5    "       " 

French  ochre  has  a  large  spreading  power,  as  it  absorbs  a  large 
quantity  of  oil,  and  it  holds  well  to  wooden  surfaces.  It  should 
be  ground  in  raw  linseed-oil,  and  if  a  thinner  is  required,  raw  oil 
should  be  used.  White  ochre  has  the  property  of  holding  well  to 
wooden  surfaces  from  the  large  amount  of  oil  taken  up  by  it,  but 
does  not  bond  well  to  any  overlying  coat  of  white  lead,  and  tends  to 
cast  it  off  by  peeling.  This  action  can  be  avoided  by  using  a  small 
percentage  of  white  lead  in  the  priming  ochre  coat. 

The  English  Oxford  and  stone  ochres  are  among  the  best  brands. 
The  Roman  ochres  grade  with  the  best  Havre,  while  the  lower  grades 
of  French  ochres  are  poor  and  possibly  lower  in  covering  power  than 
the  best  Bermuda  (Virginia)  or  other  American  brands. 

The  name  of  an  ochre  signifies,  like  all  other  paint  names,  little, 
unless  the  material  is  furnished  from  a  responsible  business  firm. 
Even  these  cheap  earths  have  to  bear  a  share  in  the  general  burden 
of  adulteration  that  is  the  order  of  the  day,  by  an  added  quantity 
of  clay,  chalk,  and  barytes  (the  latter  to  give  weight),  but  all  injure 
the  covering  power  of  the  ochre.  Their  presence  is  usually  denoted 
by  the  increased  amount  of  oil  required  to  bring  the  dry  ochre  to  a 
paste. 

There  are  many  mixtures  of  ochre  as  the  basic  pigment  for  a 
ferric  coating  other  than  those  classed  as  freight-car  colors.  One 
recommended  by  Dr.  Dudley,  and  used  to  some  extent  upon  the 
Pennsylvania  Railroad,  has  decided  superiority  over  the  general 
brands  of  iron-oxide  paints  marketed  under  the  many  alluring  and 
always  misleading  trade-names. 

Dr.  Dudley's  formula  is:  French  ochre,  39  Ibs.;  lampblack,  1  lb.; 
japan,  as  drier,  6  Ibs.;  raw  linseed-oil,  54  Ibs.  (or  6J  to  7  gallons, 


IRON-OXIDE  PIGMENTS,  UMBER.  43 

according  to  time  of  the  year  that  the  paint  is  to  be  spread).    Hot 
weather  requires  the  least  oil. 

The  better  brands  of  ochre  as  the  basic  pigment  for  freight-car 
colors  form  very  durable  paint  coatings,  whose  life  is  generally  equal 
to  that  of  the  car.  The  cheaper  grades  were  formerly  used  to  a  great 
extent  as  cheap  paints  for  tin  roofs,  but  the  large  amount  of  free  sand, 
lime,  and  other  uncombined  mineral  substances,  acids,  and  moisture 
that  they  contained,  with  the  coarse  way  they  were  calcined  and 
ground,  rendered  the  coatings  short-lived  and  unsatisfactory.  They 
required  a  large  amount  of  oil  to  spread  them,  even  with  a  white- 
wash brush.  They  dried  or  hardened  rigidly,  did  not  bond  to  the 
tin,  and  the  rate  of  expansion  and  contraction  from  the  action  of 
the  sun  was  so  materially  different  from  the  tin  they  covered  that 
they  soon  cracked,  blistered,  and  flaked  off. 

Umber. 

Umber  is  an  argillaceous  brown  hematite  ore,  essentially 
2Fe203SiO2H2O,  with  alumina  and  manganic  acid.  Specific  gravity 
2.2.  Originally  obtained  from  Umbria,  Italy,  now  chiefly  from 
Cyprus. 

As  a  pigment  it  is  used  in  both  its  raw  or  natural  state,  and  when 
calcined  is  known  as  burnt  umber.  When  calcined  at  a  low  heat  it 
turns  a  dark  brown;  a  stronger  heat  dehydrates  it,  turning  it  to  a 
red  brown  and  softening  it.  As  a  ferric  paint  it  has  no  special  quality 
other  than  the  ochres.  The  cheapness  of  the  pigment  is  more  than 
offset  by  the  amount  of  oil  it  requires  for  a  good  spreading  paint. 

Umber  is  used  as  a  drier  in  boiling  linseed-oil,  and  furnishes  an 
oil  of  good  color;  but  unless  used  in  large  quantities,  does  not  make 
so  rapid  a  drying  oil  as  the  lead,  zinc,  or  manganese  driers. 

Spanish  Brown. 

Spanish  brown,  an  iron  oxide  or  ochre,  containing  thirty  to  fifty 
per  cent  of  clay,  is  inferior  in  color  and  covering  power  to  umber, 
but  is  of  lasting  value  for  a  roofing  paint,  as  the  clay,  which  has  at 
all  times  a  strong  affinity  for  moisture,  will,  when  properly  calcined, 
take  up  seventy  to  eighty  per  cent  of  oil,  and  this  oil,  protected  from 
the  sun  and  air,  in  turn  protects  the  covered  roofing  metal  thoroughly. 
On  vertical  surfaces,  however,  less  oil  must  be  used,  else  the  coating 
will  be  liable  to  crawl  before  it  is  dry,  and  the  ochre,  not  being  so 


44  IRON-OXIDE  PIGMENTS,  SPANISH  BROWN. 

well  protected  as  on  the  horizontal  surface,  will  absorb  moisture, 
soon  corroding  the  ferric  surface.  If  two  or  more  ochre  coatings 
are  spread  over  one  another,  the  last  coating  is  liable  to  peel,  hence, 
for  tin  or  metal-covered  roofs,  one  heavy  coat  is  better  than  two  or 
more  thinner,  unless  the  latter  are  applied  after  an  interval  of  a 
year  or  more.  The  more  elastic  the  first  coating  of  this  pigment, 
the  more  durable;  but  the  greater  will  be  the  tendency  to  cast  off 
or  crack  the  second  or  other  coats. 


CHAPTER  IV. 

RED    LEAD. 

Metallic  Lead.     Symbol,  Pb.     Atomic  Weight,  206.9. 
Specific  gravity,  pure  11.445;  commercial  11.335  to  11.388. 

LEAD  occupies  an  important  part  in  the  arts  and  manufactures 
of  the  day,  and  requires  a  greater  range  of  chemical  and  mechanical 
processes  for  its  production  as  a  pigment  and  more  care  in  preparing 
and  applying  it  for  a  paint  than  any  other  pigment. 

In  its  mineral  form  it  is  associated  with  all  of  the  noble  metals, 
also  with  copper,  tin,  zinc,  bismuth,  antimony,  arsenic,  etc.  Some  of 
the  baser  metals  are  always  present  in  commercial  pig  lead,  and  affect 
the  character  of  the  pigments  prepared  from  it  by  the  processes  of 
calcination,  oxidation,  sublimation,  corrosion,  and  precipitation. 

There  are  twenty  ores  of  the  metal  known  to  the  mineralogist, 
but  metallic  lead  is  produced  from  the  five  following  minerals,  the 
analyses  of  which  indicate  not  only  the  character  of  the  ore  but  also 
of  the  metallic  lead  and  pigments  made  from  them: 

SULPHIDE  OF  LEAD,  PbS  (GALENA,  BLUE-LEAD  ORE). 

Oxide  of  lead 81 .80  to  85. 13  per  cent. 

Oxide  of  silver 0.08    "      0.02     "      " 

Oxide  of  zinc 3.59    "      2.18     "      " 

Sulphuric  acid 16.40    "    13.02     "      " 

SULPHATE  OF  LEAD,  PbSO4  (ANGLESITE). 

Oxide  of  lead 71 .00  to  72.46  per  cent. 

Oxide  of  iron 1 .00    "      0.09     "      " 

Sulphuric  acid 26 . 09    "    24 . 08     "      " 

Water 0.51    "      2.00     "      " 

CARBONATE  OF  LEAD,  PbCO3  (CERUSSITE). 

Oxide  of  lead 66 . 00  to  84 . 76  per  cent. 

Oxide  of  iron 2.30"      0.00     "      " 

Oxide  of  alumina 15 . 30    "      0 . 00     "      " 

Carbonicacid 13.00"    16.49     "      " 

Water 2.20    "      0.00     "      " 

45 


46  RED-LEAD  ORES  AND  OXIDES. 

PHOSPHATE  OF  LEAD  (PYROMORPHITE). 

Lead  (metallic) 7 . 80  to     7 . 39  per  cent. 

Oxide  of  lead 73.22    "    74.50     "      " 

Phosphoric  acid 15.76    "    15.94     "      " 

Chlorin 2.67    "      2.54     "      " 

ARSENATE  OF  LEAD  (MIMETESITE). 

Oxide  of  lead 74.96  per  cent. 

Arsenic  acid 23.06     "      " 

Chlorin 2.44     "      " 

Metallic  lead  forms  five  oxides  that  in  one  or  more  forms  are  the 
result  of  the  heat  or  chemical  changes  produced  in  the  metal  in  con- 
verting it  into  a  pigment.  They  are : 

Lead.  Oxygen. 

The  suboxide Pb2O   =  96 . 277  per  cent.       3 . 723  per  cent. 

"protoxide Pb.O=92.822     "      "         7.178     "      " 

"   red  oxide  (minium)... Pb3.O4  =  90. 630     "      "          9.370     "      " 

"   sesquioxide Pb2.O3  =  89 . 606     "      "  10 . 394     "      " 

"   dioxide  or  peroxide.  ..Pb.O4  =76.375     "      "  23.627     "      " 

Red  Lead,  or  Minium,  is  the  principal  pigment  produced  from 
the  oxides,  its  specific  gravity  being  8.5  to  8.94,  depending  upon 
the  purity  of  the  lead  "Massicot"  or  litharge,  from  which  it  is  made. 
The  color  also  depends  upon  this  point,  but  in  a  greater  degree  upon 
the  temperature  employed  in  the  oxidation  of  the  material,  the 
uniformity  of  the  heat,  the  manipulation  of  the  material  in  the  fur- 
nace, the  length  of  time  exposed  to  the  heat,  and  the  rate  and  manner 
of  cooling  down  the  furnace  and  its  contents. 

Special  furnaces  and  processes  are  required  in  its  preparation 
that  differ  materially  in  the  various  countries  where  red  lead  is  pro- 
duced, also  in  different  manufactories,  and  there  is  a  difference  in  the 
materials  employed. 

Briefly  described,  these  processes  are:  First,  by  the  cupellation 
furnace  which  converts  metallic  lead  into  litharge  in  about  24  hours. 
Second,  a  reverberatory  furnace  in  which  litharge  is  converted  into 
red  lead.  Third,  a  reverberatory  furnace  or  oven  that  reduces  metallic 
lead  into  litharge.  In  any  of  these  processes  the  litharge  is  the  first 
product,  and  is  always  formed  whenever  metallic  lead  is  heated  to 
about  900°  F.  for  about  24  hours  and  freely  exposed  to  a  current 
of  air,  the  material  being  continuously  stirred  during  the  heating 
process.  This  crude  product  or  litharge  is  a  coarse  granular  substance 
that  upon  further  heating  is  fused  into  a  crystalline  mass.  When  cold 


RED-LEAD  MANUFACTURE.  47 

this  mass  when  broken  up  is  in  the  form  of  thin  yellow  or  brown 
scales,  and  in  this  state  is  known  as  flake  or  glass-makers'  litharge. 
This,  when  ground  in  water  and  dried,  changes  its  color  to  a  buff,  and 
is  the  ordinary  commercial  litharge. 

When  the  crude  litharge  powder  is  again  moderately  heated  in  a 
reverberatory  furnace  or  oven  and  exposed  to  a  current  of  air  with 
continuous  stirring  for  from  26  to  48  hours,  or  until  a  sample  drawn 
at  a  low  red  heat  appears  of  a  dark-red  color  turning  to  a  bright  red 
on  cooling,  the  furnace  is  closed  and  allowed  to  cool  slowly;  a  con- 
dition most  essential  to  success  in  the  cglor,  that  if  not  satisfactory, 
requires  a  reheating  and  cooling  of  the  product  now  known  as  red  lead. 

Red  lead  made  from  litharge  (from  the  imperfect  oxidation  of 
the  litharge)  contains  a  larger  amount  of  the  protoxide  of  lead  than 
that  made  from  the  carbonate  or  white  lead,  where,  on  account  of 
the  finer  condition  of  the  material,  the  oxidation  is  more  complete, 
more  quickly  effected,  and  generally  of  a  better  color  and  quality. 

With  this  complex  chain  of  operations  there  are  many  trade 
secrets  to  secure  not  only  a  uniform  quality  of  the  pigment,  but  its 
color.  The  latter  nearly  always  remains  an  uncertain  element  even 
with  the  best  of  attention  given  during  the  whole  process. 

Red  lead  is  found  native  in  many  localities  mixed  with  the  other 
ores  of  lead,  probably  resulting  from  their  oxidation  by  natural  causes. 
Chromate  of  lead  (Pb.CrO4.  Specific  gravity,  4.6  to  5.2),  the  neutral, 
or  meta-chr ornate,  known  as  crocoisite  or  lehmanite,  is  a  native  red-lead 
ore  found  in  commercial  quantities  in  many  parts  of  the  world.  It  is 
in  the  form  of  translucent  crystals  of  a  yellow  color  with  various 
shades  of  other  colors,  and  is  associated  with  decomposed  gneiss  and 
granite.  The  method  of  converting  these  red-lead  ores  into  pigments 
need  not  be  described  here.  All  of  the  yellow  and  red  chromates  of 
lead  are  obtained  from  crocoisite.  They  are  strong  colors,  and  do 
not  decompose  on  exposure  to  the  air  or  light. 

Red  lead  is  one  of  the  heaviest  and  most  expensive  pigments, 
also  the  most  difficult  to  prepare  for  a  paint  or  to  spread.  It  is  more 
susceptible  to  adulteration,  and  is  more  adulterated  by  interests  inimi- 
cal to  its  reputation,  than  any  other  pigment,  with  the  possible  excep- 
tion of  its  sister-product,  white  lead.  There  are  many  well-authen- 
ticated instances  of  its  perfect  protection  of  important  structures, 
and  a  great  number  of  its  failure  in  locations  where  the  failure  can 
be  directly  traceable  to  causes  detrimental  to  the  success  of  any 
pigment.  It  has  been,  and  is,  condemned  for  causes  directly  trace- 


48  RED-LEAD  ADULTERATIONS. 

able  to  its  improper  preparation  and  application,  and  where  the 
failure  should  have  been  foreseen  by  the  engineer  or  master  painter, 
and  where  carelessness,  indifference,  or  ignorance  of  the  conditions 
to  which  the  coating  was  to  be  subjected,  were  the  prime  factors  of 
its  non-success. 

When  obtained  from  a  reputable  manufacturer  and  properly 
prepared  with  a  suitable  vehicle  and  spread  under  known  condi- 
tions of  its  future  service,  it  has  proved  to  be  one  of  the  most  reliable 
pigments.  Its  color  is  distinctive,  hence  it  is  not  favorable  to  the 
use  of  adulterants.  Brick-dust,  iron  oxide,  and  barytes  tone  down 
its  high  color,  but  are  detrimental  in  all  other  respects.  Chalk, 
gypsum,  and  other  light-color  and  low-specific-gravity  substances 
are  often  added  to  correct  the  tendency  of  red-lead  paint  to  "set" 
in  the  paint-pot  while  applying  it,  or  to  prevent  its  "creep"  when 
spread  upon  vertical  or  inclined  surfaces.  All  such  adulterants  are 
easily  detected ;  they  do  not  prevent  the  set  or  crawl  of  the  paint, 
and  are  the  principal  cause  of  the  failure  of  the  coating.  For  the 
foundation  coat  upon  ferric  bodies,  it  will  cover  about  as  much 
surface  as  any  other  paint  applied  under  the  same  conditions  and 
with  the  same  effort  on  the  part  of  the  painter  to  brush  it  out.  The 
latter  factor  is  frequently  too  small  to  ensure  success  with  even  a 
whitewash. 

As  a,first  coat  on  ferric  bodies,  applied  at  the  workshop,  its  color 
shows  at  once  any  material  injury  to  the  coating  due  to  the  usual 
handling  and  transportation,  also  readily  indicates  if  the  grease  and 
dirt  due  to  the  machining  processes  in  the  shop  or  received  during 
transportation  and  erection  have  been  properly  attended  to  or  not. 
It  is  a  prime  watch-dog  in  this  respect. 

Its  tendency  to  settle  in  the  paint-pot,  also  "to  set,"  and  the 
necessity  for  constantly  stirring  it  up  by  the  painter,  probably  lessens 
by  a  small  amount  the  number  of  square  feet  of  surface  he  can  spread 
in  a  day.  This  is  probably  an  objection  to  its  use,  but  is  offset  by 
the  many  points  in  its  favor.  The  rapid  set  of  red  lead  when  mixed — 
a  peculiarity  of  this  pigment — is  as  objectionable  in  a  paint  before 
it  is  applied  to  the  surface  as  the  set  or  hardening  of  hydraulic  cement 
on  the  mortar-board.  When  either  the  paint  or  mortar  has  set  before 
being  spread,  it  is  useless  for  its  intended  purpose.  If  the  set  of  either 
is  broken  up  by  stirring  and  they  are  then  applied,  both  may  appear 
to  be  of  the  same  nature  as  before  setting,  but  they  are  injured  beyond 
recovery.  The  mortar  will  not  be  much  better  than  a  wetted  sand, 


SETTING  OF  RED  LEAD.  49 

and  will  not  again  bond  the  sand  or  to  the  masonry.  The  red  lead 
will  not  recover  its  combining  power  that  ensures  the  mutual  bond 
between  the  atoms  of  the  pigment  and  to  the  surface  covered,  be  it 
wood  or  metal.  When  in  this  condition,  if  it  is  applied  to  a  metallic 
surface,  it  "crawls,"  as  it  is  called,  and  presents  an  appearance  more 
like  that  of  curdled  milk  than  a  paint,  and  the  actual  protection  of 
the  body  covered  is  due  to  the  vehicle  only.  It  will  add  but  little 
to  the  covering  power  other  than  what  any  adulterating  substance 
would  do. 

The  setting  of  red  lead  is  due  to  two  chemical  reactions,  namely, 
a  combination  between  the  litharge  of  the  red  lead  and  the  glycerine 
element  in  the  oil ;  also  a  combination  between  the  fatty  acids  of  the 
oil  and  the  litharge,  forming  a  lead  soap,  quite  a  firm  substance,  but 
one  not  favorable  to  the  durability  of  the  paint. 

Many  of  the  failures  of  red-lead  coatings,  if  rigidly  traced  to  their 
source,  would  no  doubt  be  found  to  have  been  caused  by  the  care- 
lessness of  the  painter  in  not  keeping  the  paint  well  stirred  during 
its  application,  or  in  preparing  too  large  a  quantity  for  immediate  use, 
or  by  using  the  paint  left  over  from  day  to  day,  or  from  another  job. 

Red-lead  and  Lampblack  Mixtures  to  Delay  "Setting" 

Iron  oxide,  zinc  oxide,  barytes,  gypsum,  etc.,  added  to  red  lead  to 
prevent  "setting,"  are  objectionable  and  ineffective,  as  before  noted. 
Lampblack  from  J  to  1  ounce  per  pound  of  red  lead  delays  the  set- 
ting action  and  enables  the  red  lead  to  be  prepared  as  a  paste  to  be 
used  in  the  immediate  future,  when  it  is  thinned  by  additional  oil  at 
the  time  and  place  of  using.  The  bright  red  of  the  minium  is  modi- 
fied by  the  lampblack  to  a  chocolate  color  that  may  be  light  or  dark 
according  to  the  quantity  of  the  lampblack  used.  Lampblack  of 
itself  is  an  excellent  pigment,  is  electrically  passive  or  neutral  to  all 
pigments,  and  by  natural  formation  is  so  finely  divided  that  it  mixes 
easily  and  thoroughly  with  the  oil  and  red  lead  without  deteriorating 
the  quality  of  either. 

Many  painters  have  reported  a  difficulty  with  the  use  of  red  lead 
and  lampblack:  that  with  1  ounce  of  lampblack  per  pound  of  red 
lead  the  paint  would  not  dry  promptly  for  shop  work  without  the 
use  of  japan  or  turpentine  driers.  Bridge  engineers,  however,  report 
that  red-lead  paints  carrying  10  ounces  of  lampblack  to  12  pounds 
of  red  lead  have  stood  for  three  or  four  months  without  setting  or 


50  RED-LEAD  AND  LAMPBLACK  MIXTURES 

hardening  by  simply  agitating  or  rolling  the  barrels  daily.  In  one 
case  the  paint  barrels  were  left  undisturbed  for  four  months,  and 
though  the  red  lead  had  settled  in  some  degree,  when  it  was  stirred 
again  the  paint  spread  as  well  and  dried  as  firmly  as  though  freshly 
mixed. 

Lampblack  containing  sulphur  in  any  appreciable  amount  should 
never  be  mixed  with  red  lead  for  a  coating.  Ground  soot  from  chim- 
neys or  furnace-flues,  ground  bituminous  coal  or  coke,  or  the  soot  from 
most  of  the  petroleum  or  heavy  mineral  oils,  contain  sulphur  enough 
to  cause  the  prompt  failure  of  a  red-lead  coating,  even  when  used  to 
the  amount  of  J  of  an  ounce  per  pound  of  red  lead. 

Mr.  Ball,  master  painter  Pennsylvania  Railroad,  1897,  reported 
the  result  of  some  of  his  experiments  with  "protective  paints  for 
metallic  parts  of  cars  and  trucks,"  viz.: 

First.  Red  lead  and  raw  linseed-oil,  with  litharge  as  a  drier. 
Second.  Red  lead  and  raw  linseed-oil,  no  drier. 
Third.  Red  lead  and  lampblack,  equal  parts. 
Fourth.  Red  lead  one  part,  lampblack  three  parts. 
Fifth.  Mineral  brown  (red  oxide  of  iron;. 
Sixth.  Mexican  graphite. 

All  paints  were  mixed  from  the  same  quality  of  raw  linseed-oil; 
none  but  the  first  had  any  drier. 

At  the  end  of  fifteen  months  of  atmospheric  exposure  at  the  car 
shops  their  condition  was  as  follows: 

Number  One  had  failed  in  two  or  three  spots. 

"         Two  was  intact  and  appeared  to  be  in  condition  to  resist 

a  number  of  years'  wear. 

"         Three  had  scaled  off  in  a  number  of  places,  showing  rust. 
"         Four  was  in  a  still  worse  condition. 
"         Five  was  completely  gone. 

"         Six  was  in  perfect  condition,  the  same  as  the  straight  red- 
lead  sample. 

The  slow  setting  and  drying  mixtures  of  red  lead  and  lampblack 
are  probably  better  for  field  work,  where  slow  drying  is  of  little  moment, 
unless  bad  weather  conditions  are  to  be  met,  than  for  use  at  the  shops 
where  the  transportation  requirements  govern.  Thinning  the  red- 
lead  and  lampblack  paste  with  boiled  oil  when  the  paint  is  applied 
will  add  the  necessary  drying  element  to  the  paint  without  the  use  of 
turpentine. 


RED-LEAD  AND  LAMPBLACK  MIXTURES,  51 

Spirits  of  turpentine  is  objectionable  in  all  paints,  as  its  evapo- 
ration leaves  the  coating  more  porous  than  it  would  be  if  the  paint 
dried  naturally;  and  it  deadens  the  gloss.  Japan  driers  for  red-lead 
paints  are  less  objectionable  than  the  turpentine.  They  are  heavier 
and  add  resinous  matter  to  the  paint  in  drying  that  is  of  the  same 
character  as  the  vehicle  with  which  the  red  lead  is  ground.  The 
drying  of  japan  is  principally  by  resinification  and  not  wholly  by 
evaporation,  as  is  the  case  with  turpentine;  with  the  added  japan 
the  period  of  drying  can  be  governed  as  required  by  using  a  small 
proportion  of  raw  linseed-oil. 

Excerpts  from  a  trade  catalogue  *  relative  to  the  use  of  turpen- 


FIG.  8.— Dried  film  of  red  lead  encrusted  with  rust  X 100.     Taken  from  a  painted 
structure  which  showed  no  rust  on  surface.     (M.  Toch.) 

tine  and  red  lead  say:  "We  are  not  prepared  to  advise  the  use  of 
turpentine  in  shipyards,  where,  owing  to  time  contracts,  it  is  often 
necessary  to  paint  in  damp  or  freezing  weather,  though  the  practice 
in  the  Marine  Department  of  the  Maryland  Steel  Co.  from  many 
years'  experience  in  the  use  of  red  lead  is,  viz.:  Use  three  parts  of 
linseed-oil  (raw,  presumably)  and  one  part  of  turpentine  for  the  first 
and  second  coats,  with  sufficient  drier  (presumably  japan)  to  set 
well  in  twenty-four  hours,  allowing  five  to  six  days  between  the 
coats.  The  third  coat  to  be  an  oil  coat  without  drier." 

*  "How  to  Use  Red  Lead."     National  Lead  Company. 


52  RED-LEAD  PAINT  MIXTURES. 

"Theoretically,  and  for  dry,  bright  weather,  red  lead  should 
be  used  with  raw  linseed-oil  and  no  drier,  red  lead  itself  being  a  natural 
drier.  By  so  doing,  the  chemical  union  between  the  pigment  and 
oil  is  most  complete  and  the  resultant  paint  is  more  durable.  How- 
ever, for  ordinary  service  add  a  small  quantity  of  japan  or  use  boiled 
linseed-oil.  By  so  doing  a  more  viscous  vehicle  is  had,  which  better 
sustains  the  heavy  particles  of  the  red  lead,  thereby  preventing  its 
running  on  vertical  surfaces,  and  possibly  giving  greater  covering." 

Red-lead  Paint  Mixtures. 

Many  railway  engineers  favor  the  following  mixture  of  red-lead 
paint  for  their  structures  where  the  time  of  drying  is  of  little  moment. 
For  the  first  or  priming  coat,  20  pounds  of  red  lead  and  1  gallon  of  raw 
linseed-oil.  No  driers.  For  the  second  and  third  coats:  a  paste 
made  from  60  pounds  of  hydrated  sulphate  of  lime,  30  pounds  of  lamp- 
black, 5  pounds  of  red  lead,  making  100  pounds  of  pigments,  to  which  20 
gallons  of  boiled  linseed-oil  are  added,  making  30  gallons  of  paint. 
This  makes  a  fair  drying  paint  of  a  dark  or  dirty  grayish-brown  color, 
weighing  about  8J  pounds  per  gallon.  All  of  the  power  in  this  paint 
to  prevent  corrosion  lies  in  the  red  lead  and  lampblack,  the  sul- 
phate of  lime  adds  the  stuffing  for  quantity  without  contributing 
anything  of  a  protective  character  to  the  mixture,  and  the  covering 
power  is  poor. 

If  any  of  the  low-carbon  amorphous  graphites  were  substituted  for 
the  sulphate  of  lime  in  this  formula,  the  paint  would  be  better  in 
all  respects  for  coating  ferric  bodies. 

Mulder's  Experiments  with  Cheap  Red-lead  Paints. 

Mulder,  in  his  experiments  to  produce  a  cheap  paint,  used  boiled 
linseed-oil  containing  2J  per  cent  of  red  lead.  He  used  100  parts 
of  this  oil  with  every  one  of  the  following  mixtures.  The  iron  oxide 
used  was  Carrier's  (Belgium),  that  analyzed  as  follows: 

Iron  oxide 68.27  per  cent  =  47.79  per  cent  of  metallic  iron. 

Clay 27.00 

Marl 0 . 27     '  ^  27 . 67     "      "     mineral  substances. 

Chalk 0.40 

Water 2.75 

Undetermined.  ...   1.31 

100.00     "      " 


CHANGES  IN   RED-LEAD  PAINT,  ACTION  OF  SULPHUR,      53 

200  parts  of  pulverized  fine  sand,  5  parts  red  lead,  gave  a  paint 
of  some  merit. 

Red  lead  25  per  cent,  iron  oxide  40  per  cent,  gave  a  very  good 
coating. 

20, 40, 60,  parts  of  red  lead  to  100  parts  of  iron  oxide  gave  excellent 
results.  20  to  90  parts  of  red  lead  to  50  parts  of  pulverized  red 
roofing  tiles  gave  a  thick  heavy  coating. 

40  parts  of  red  lead  and  100  parts  of  pulverized  red  roofing  tiles 
gave  an  excellent  coating. 

20  to  90  parts  of  red  lead  and  100  parts  of  pulverized  ironstone 
gave  a  paint  of  distinguished  excellence. 


FIG.  9. — Photomicrograph  X 1 00  of  a  film  of  red-lead  paint  showing  grains  of 
various  sizes,  all  more  or  less  encysted  with  air-bubbles.     (M.  Toch.) 

Other  mixtures  of  red  lead  favorably  reported  upon  by  experi- 
menters are  red  lead,  zinc  oxide,  and  Blanc-Fixe.  The  latter  sub- 
stance serves  to  hold  up  the  red  lead  in  the  mixture  during  the  first 
stage  of  drying  and  prevents  its  "  creep."  Amorphous  graphite 
is  also  used  instead  of  the  Blanc-Fixe  for  the  same  purpose.  None 
of  these  substances  or  any  others  employed  for  this  purpose  oan  be 
so  mixed  that  they  will  not  be  subject  to  the  influences  that  destroy 
all  compounded  paints,  as  mentioned  elsewhere  in  this  work.  (See 
Chapters  XXVII  and  XXXII.) 


54      CHANGES  IN  RED-LEAD  AND  ZINC-OXIDE  MIXTURES. 

The  bright  lustre  of  red  lead  is  often  toned  down  by  Venetian 
red.  This  pigment,  if  it  could  be  obtained  from  a  natural  ore,  is  a 
very  desirable  one,  but  the  mines  that  furnished  it  in  former  days 
have  long  been  exhausted  as  a  commercial  source  of  supply,  and 
the  copperas  reds  have  taken  its  place.  These  contain  a  large  amount 
of  sulphuric  acid  loosely  held  in  combination  (see  Analysis,  Chapter 
III),  and  their  use  with  red  lead  is  as  disastrous  to  the  paint  as  the 
direct  effect  of  hydric  sulphide. 

The  effect  of  the  sulphur  element  in  both  cases  is  greatly  influenced 
by  heat,  a  few  weeks'  exposure  to  hot  summer  temperatures  being 
all  that  is  necessary  to  destroy  the  coating  by  rendering  it  brittle 
and  easily  removed  by  the  hand,  or  else  causing  it  to  peel  in  strips. 
This  action  of  the  sulphur  is  sometimes  said  not  to  be  due  to  a  change 
for  the  worse  in  the  red-lead  atoms,  but  to  the  change  in  the  ve- 
hicle. But  the  effect  of  sulphur  upon  dried  linseed-oil  is  almost 
nil,  and  the  oil-film  is  always  nearly  transparent  of  itself,  whatever 
pigment  may  be  associated  with  it.  Any  change  in  the  pigment 
is  denoted  by  a  change  of  color  in  the  paint,  whatever  may  be  the 
cause  of  the  change.  The  change  in  the  pigment  simply  shows 
through  the  thin  film  of  dried  oil  quite  as  readily  as  though  it  were 
of  glass,  and  generally  indicates  a  speedy  dissolution  of  the  coating. 
In  many  mills  and  workshops  all  of  these  conditions — heat,  sulphurous 
fumes,  and  saturated  atmospheric  elements — are  present,  and  red-lead 
coatings  in  such  locations  are  short-lived. 

The  sulphur  element,  whether  in  the  oil  or  the  red  lead,  or  from 
any  other  source,  renders  the  paint  liable  to  dry  on  the  surface  only, 
and  the  inner  portion  of  the  oil  that  encloses  the  pigment-atoms 
remains  soft  and,  therefore,  more  sensitive  to  any  destructive  influ- 
ences that  reach  the  coating. 

From  28  to  30  pounds  of  red  lead  to  a  gallon  of  oil  are  necessary 
to  make  a  good  red-lead  paint,  for  even  when  well  ground  it  is  liable 
to  streak,  curdle,  or  run,  and  is  difficult  for  the  painters  to  spread. 
The  bulk  of  the  red  lead  is  so  small  compared  with  an  equal  weight 
of  any  other  pigment  per  unit  of  covered  surface,  that  the  atoms  of 
the  red  lead  are  well  housed  in  the  oil  and  better  protected.  Hence, 
when  the  conditions  are  favorable  for  a  red-lead  coatine,  it  proves  to 
be  a  ^  more  durable  one  than  coatings  made  from  other  pigments 
that  carry  (as  many  of  them  do)  in  their  composition  the  elements 
for  their  dissolution. 

Fig.  10  illustrates  the  character  of  red-lead  coatings  when  not  well 


CHANGES  IN  RED-LEAD  AND  ZINC-OXIDE  MIXTURES.     55 

worked  or  brushed  out  in  spreading.     The  porous  character  would 
disappear  when  spread  on  any  surface  other  than  glass. 

The  United  States  and  other  Governments  have  favored  in  the 
past  a  mixture  of  two  or  three  parts  of  red  lead  and  one  of  zinc  oxide 
for  the  protective  covering  for  lighthouses  and  seacoast  iron  struc- 
tures. These  coatings  are  harder  than  red  lead  alone,  and  better 
lesist  the  action  of  salt-water  spray,  fog,  and  the  abrasion  from  the 
sand-blast  usual  in  such  locations.  But  the  result  of  some  thirty 


FIG.  10. — Photomicrography  100  of  red  lead  and  oil  taken  from  a  paint-pot 
and  dried  on  a  slide.  The  film  is  filled  with  air-bubbles  and  the  coat  is 
transparent  in  spots,  although  to  the  eye  it  looks  solid.  (M.  Toch.) 

years'  experience  with  these  mixtures  has  led  to  their  abandonment 
for  the  reason  that  the  oxide  of  zinc  in  the  coating  changed  to  a  car- 
bonate of  zinc,  and  by  its  increase  of  volume  disrupted  the  dried  coat- 
ing, exposed  the  ironwork,  and  the  increase  in  the  corrosion  was 
markedly  greater  than  with  red  lead  alone,  or  red  lead  and  silica, 
or  red  lead  and  graphite  coatings. 

Red-lead  coatings  soften  metallic  tin,  hence  for  tin  roofs  they 
have  not  proven  so  durable  as  iron-oxide  or  graphite  coatings,  and 
are  too  expensive  for  that  purpose.  The  effect  of  the  red  lead  for 
such  purposes  is  to  form  a  white  oxide  of  tin  by  the  galvanic  action 
between  the  two  metals.  The  oxide  of  tin  is  free,  and  having  no 
vehicle  incorporated  with  it,  is  easily  washed  out  by  storms,  leaving 
the  iron  plate  entirely  unprotected. 


56  RED-LEAD  MIXTURES. 

Fig.  11  illustrates  the  action  of  a  red-lead-compound  paint  showing 
the  character  of  that  class  of  coatings  for  the  protecting  of  surfaces, 
especially  a  ferric  one. 

Red-lead  compositions  are  extensively  advertised  to  keep  indefi- 
nitely without  setting,  and  that  are  ready  for  use  at  any  time  without 
further  mixing  or  preparation.  In  all  such  mixtures,  the  red  lead, 


FIG.  11. — Photomicrograph  X 100  of  a  film  of  dried  paint  taken  from  an  iron 
pillar  showing  rust  blisters.  The  dark  spot  is  red  lead  and  a  fissure 
runs  through  the  centre.  The  zinc  oxide  and  white  lead  are  white  and  are 
intact.  (M.  Toch.) 

or  the  oil,  or  both,  are  adulterated  and  will  be  found  to  be  compara- 
tively short-lived  and  unreliable  whatever  may  be  the  guarantee, 
which  in  general  lays  more  stress  upon  the  extraordinary  large  surface 
that  can  be  covered  than  the  permanent  character  of  the  coating. 
As  well  expect  a  hydraulic  cement  ready  mixed  to  be  a  suitable  article 
for  engineering  use  as  an  " always-ready"  red-lead  paint. 

The  setting  or  solidification  of  a  pure  or  nominally  pure  red-lead 
paint  is  a  characteristic  chemical  union  between  the  oil  and  the  lead, 
and  without  this  action  the  paint  is  worthless.  This  chemical  action 
is  sought  to  be  simulated  in  all  compound  paints  by  the  liberal  use 
of  driers  either  incorporated  in  the  vehicle  by  heat  or  by  being 
introduced  through  the  bung-hole  of  the  barrel.  The  setting  must 
take  place  eventually,  and  the  better  paint  will  be  the  one  in  which 
it  is  definitely  provided  for,  and  not  left  to  the  haphazard  operations 
around  the  bung-hole. 


RED-LEAD  MIXTURES  READY  FOR  USE.  57 

One  gill  of  crude  mineral  oil  or  heavy  refined  petroleum  added 
to  a  gallon  of  red-lead  paint  will  delay  the  setting  of  it  indefinitely. 
It  will  dry  superficially,  as  the  oxidizing  power  of  the  red  lead  will 
ensure  that  essential,  but  the  petroleum  will  always  remain  viscid  in 
the  coating  and  eventually  destroy  it  by  peeling  soon  after  an  exposure 
to  a  strong  sunlight  or  heat,  following  or  followed  by  a  lower  damp 
temperature  or  a  storm. 

Red  lead,  either  in  the  form  of  a  pigment  or  paste,  when  quoted 
as  being  "  second  quality,"  can  be  regarded  not  only  with  suspicion, 
but  with  a  certainty  that  it  is  greatly  adulterated  or  poorly  oxidized 
from  impure  lead,  or  not  properly  washed  or  pulverized. 

First-class  manufacturers  of  red  lead  have  no  second-quality 
product  that  they  are  willing  to  have  bear  their  brand  or  seal.  There 
are  a  large  number  of  red-lead  corroders  in  the  United  States,  and 
to  the  author's  knowledge  only  one  of  the  number  advertises  a  second- 
class  product.  It  may  also  be  of  interest  to  note  that  the  United 
States  Bureau  of  Construction,  in  its  orders  for  red  lead,  specifies 
the  make  of  one  corroder  as  the  standard  of  quality  to  which  all 
tenders  must  conform. 

A  good  red  lead  as  it  comes  from  the  manufacturer  is  finely  pul- 
verized, as  this  point  in  a  great  measure  governs  the  setting  and 
running  (creep,  crawl,  or  curdling  the  painters  call  it).  The  atoms 
should  be  opaque,  which  indicates  a  good  covering  or  light  dispersing 
power.  If  the  atoms  are  crystalline  and  more  or  less  trans- 
lucent, the  paint  will  have  a  tendency  to  "tack."  This  effect  does 
not  always  indicate  that  the  pigment  is  deficient  in  other  respects  to 
form  a  durable  coating;  for  the  "tack"  is  sometimes  due  to  the  quality 
of  the  oil,  and  that  the  red-lead  manufacturer  has  seldom  anything 
to  do  with. 

The  adulteration  of  red  lead  and  litharge  can  be  readily  ascer- 
tained by  digesting  a  sample  in  a  warm  solution  of  nitric  acid;  the 
adulterants  will  remain  undissolved. 

Boiling  hydrochloric  acid  will  extract  the  iron  oxide  from  the 
residue.  If  adulterated  red  lead  is  ignited  there  remains  a  mixture  of 
yellow  lead  oxide  and  the  red  or  other  colored  substances  that  have 
been  added  to  the  red  lead. 

Red  lead  boiled  in  hydrochloric  acid  is  slowly  converted  into  the 
chloride  of  lead  with  an  evolution  of  chlorine  gas.  Dilute  nitric 
acid  only  slowly  dissolves  red  lead,  leaving  a  brown  powder. 


58  RED-LEAD  ADULTERATIONS  AND    TESTS. 

Salt  creates  a  chemical  action  on  red  lead  that  is  liable  to  blister 
the  coating  and  reduce  the  red  lead  to  a  metallic  state. 

Grimshaw  recommends  a  mixture  of  red  lead  with  painters' 
sizing  to  cover  pine  knots  or  yellow  pine  woodwork,  instead  of  the 
usual  shellac  varnish.  It  forms  a  heavier  coating  than  shellac,  is 
equally  or  more  resistant  to  the  pitch,  and  is  less  liable  to  blister. 

A  gallon  of  pure  linseed-oil  will  require  not  less  than  20  pounds 
as  a  minimum  quantity  of  pure  red  lead  to  30  pounds  as  a  maximum 
quantity  for  a  reliable  red-lead  paint  which  will  cover  from  750  to 
1200  square  feet  of  metallic  surface.  These  quantities  of  material 
at  once  remove  red-lead  paint  from  any  comparison  of  cost  with 
the  oxide-of-iron  and  many  mixed  paints — principally  in  the  form 
of  proprietary  goods,  the  ingredients  of  which  are  only  known  to  the 
makers,  and  the  character  and  performance  of  which  will  vary  in 
quite  as  erratic  a  manner  as  the  price  paifi  for  them. 

The  protective  qualities  of  a  well-oxidized  pure  red-lead  and  a 
pure  oil  paint,  properly  applied  to  any  structure  under  any  exposure, 
except  to  the  action  of  hydric-sulphide  gas,  cannot  be  gainsaid.  But 
what  effect  other  than  failure  of  it  can  be  expected  when  a  govern- 
ment engineer  in  charge  of  an  important  hydraulic  construction, 
after  cleaning  the  metal  part  of  the  work  by  the  sand-blast,  coated 
it  with  the  following  paint?  "Red  lead,  40  pounds,  mixed  with  three 
pints  of  water  to  one  gallon  of  raw  linseed-oil  for  the  first  coat,  and 
for  the  second  coating,  red  lead,  40  pounds,  three  pints  of  water, 
three  ounces  of  lampblack  mixed  with  enough  turpentine  to  make 
a  paste,  and  one  gallon  of  raw  linseed-oil.  It  was  found  necessary 
to  first  moisten  the  red  lead  with  water  to  prevent  the  paint  from 
streaking  and  sagging.  Without  the  water,  a  large  proportion  of 
turpentine  and  drier  would  have  been  necessary,  and  this  was  con- 
sidered injurious  to  the  life  of  the  paint.  In  warm  weather  a  slightly 
less  quantity  of  red  lead  could  be  used"  (or  more  water?). 

Many  kindred  examples  of  such  "how  not  to  protect"  structures 
can  be  cited,  none,  however,  more  conspicuous  than  the  above  when 
the  engineer  in  charge  and  the  character  of  the  work  are  considered. 

The  substitution  of  water  for  turpentine  in  the  amount  here 
noted  in  order  to  prolong  the  life  of  the  paint  will  be  welcome  news 
to  the  many  manufacturers  of  that  class  of  patent  or  proprietary 
paints  who  have  heretofore  deemed  an  addition  of  20  to  25  per  cent 
of  water  to  the  7  to  8  per  cent  present  in  their  green  linseed-oil  as 
about  the  limit  of  a  whipped-in-oil  vehicle.  They  can  now  proceed 


LITHARGE,  QUALITIES  AND  ANALYSIS.  59 

to  water  their  stock  of  paint  to  a  point  where  even  the  water  in  the 
financial  part  of  their  enterprise  will  seem  in  comparison  but  an 
insignificant  pool.  (The  effects  of  watered  oil  is  further  considered 
in  Chapter  XXV.) 

Litharge,  PbO  (Protoxide  of  lead).     Specific  gravity,  8.50  to  9.00. 

Litharge  as  the  first  product  in  the  oxidation  of  metallic  lead 
to  form  red  lead  has  been  described.  Another  source  of  litharge  is 
from  the  scum  of  melted  lead  or  that  from  the  smelting  of  silver- 
bearing  ores.  It  is  formed  as  an  oxide  by  exposing  to  the  roasting 
heat  of  a  furnace  the  slag,  or  "matte,"  that  on  cooling  forms  into 
white  or  flake  litharge.  The  part  that  hardens  last  is  called  "  Massi- 
cot "  or  "levigated"  litharge,  and  is  ground  in  water,  dried,  and 
made  ready  for  the  market.  It  is  a  yellowish-red  substance  or  an 
amorphous  powder,  and  crystallizes  in  fine  six-sided  scales  or  plates. 
It  is  a  yellow  or  reddish  protoxide  of  lead,  partially  fused  and  semi- 
transparent.  The  yellow  is  the  fused  or  hard  pieces  that  require  to 
be  ground  and  levigated;  the  red  atoms  are  the  flakes.  The  difference 
in  the  color  arises  from  the  mechanical  condition  resulting  from  the 
manner  and  difference  in  cooling  the  roasted  product,  a  rapid  cooling 
giving  a  yellowish  color,  a  slow  cooling  a  reddish  one. 

By  analysis  it  consists  of  the  protoxide  of  lead,  (PbO), 

94 . 68%  to  96 . 20%  =  89 . 28%  to  87 . 86%  of  metallic  lead. 
6.93%    "     6.82%  of  oxygen. 

2.89%   "    traces      "  the  oxides  of  iron,  zinc,  copper,  antimony,  bismuth,  etc. 
4.36%    "    traces      "  arsenious,  silicic,  and  carbonic  acids. 
0.49%   "    traces      "  lime. 

The  special  furnaces  employed  and  the  manipulations  of  the 
charge  during  the  heating  and  cooling  processes  applicable  to  the 
manufacture  of  red  lead  are  requisite  for  a  reliable  litharge;  also 
the  same  care  in  grinding  and  the  subsequent  operations  to  prepare 
it  for  a  pigment  or  for  other  uses.  Its  integrity  when  used  in  a  paint 
is  affected  by  the  same  causes  that  affect  a  red-lead  coating.  It  is 
adulterated,  if  possible ,  in  a  more  barefaced  manner  than  any  red 
lead. 

Orange  mineral  is  made  from  the  litharge  "Massicot,"  also  from 
white  lead.  In  many  cases  refuse  white  lead  is  used  as  the  base 
material.  The  material  is  placed  in  a  reverberatory  furnace  and 
exposed  to  a  moderate  heat  and  a  current  of  air  and  stirring  as  usual 
for  producing  red  lead. 


60  ORANGE  MINERAL. 

The  carbonic  acid  in  the  white  lead  is  expelled,  leaving  a  protoxide 
of  lead  which  absorbs  more  oxygen  and  produces  a  red  lead  of  a 
lighter  color  than  that  made  from  litharge  by  reason  that  the  oxida- 
tion is  more  complete. 

Paris  red  is  prepared  by  roasting  the  carbonate  of  lead  to  a  litharge, 
the  difference  between  the  Orange  mineral  and  Paris-red  pigments 
being  that  the  latter  retains  a  little  carbonic  acid  in  its  composition 
due  to  the  different  degree  of  heat  employed  in  the  furnace  and  the 
manner  of  cooling  the  product.  Vermilionette  is  an  orange-red 
pigment  formed  from  the  oxide  of  lead. 


CHAPTER  V. 

WHITE     LEAD. 

White    Lead,    PbCO3    (Hydrated     Carbonate    of    Lead).      Specific    gravity, 

6.465  to  6.480. 

THE  native  anhydrous  meta-carbonate  of  lead,  (PbCO3),  called 
white-lead  ore  or  cerussite,  when  pure  is  found  in  colorless  crystals 
of  the  trimetric  system.  It  is  found  in  commercial  quantities  in  all 
parts  of  the  world  where  mineral  lead  ores  are  mined  for  smelting  pur- 
poses. Pliny  mentions  the  use  of  a  native  ceruse  found  on  the  lands 
of  Theodotus  at  Smyrna. 

The  proto-sulphide  of  lead,  (PbS),  is  the  blue-lead  ore  (Galena)  and 
is  the  principal  source  for  the  supply  of  metallic  lead.  White  lead 
and  the  red  oxide  of  lead  are  next  to  the  oxide  of  iron,  ochre,  um- 
ber, and  sienna,  the  oldest-known  pigments.  Dioscorides  (B.C.  400)^ 
Pliny,  and  Vetruvius  all  mention  the  production  of  white  lead  by 
exposing  metallic  lead  to  the  vapor  of  vinegar,  giving  the  product  the 
name  of  "Cerusa"  and  "Cerosa."  Bergman  in  1775  localized  it  as 
a  carbonate  of  lead  instead  of  an  acetate,  as  it  had  before  been  con- 
sidered. 

White  lead  was  used  by  the  Egyptians  as  a  cosmetic  long  before 
its  employment  for  a  pigment. 

The  mining  and  smelting  of  lead  ore  to  produce  metallic  lead  were 
practised  by  the  Chinese  2000  years  B.C.  In  the  smelting  of  lead 
ore  large  quantities  of  the  lead  are  oxidized  to  the  red-lead  "  minium," 
the  use  of  which  as  a  pigment  antedates  the  knowledge  of  producing 
white  lead  by  corrosion.  Moses  commanded  the  Israelites  to  purify 
lead  (called  opheret)  by  fire. 

The  principal  amount  of  white  lead  is  produced  by  the  so-called 
"Old  Dutch  Process."  This  process  did  not  originate  in  Holland, 
where  the  recorded  establishment  of  it  does  not  appear  before  the 
sixteenth  century.  It  was  probably  introduced  into  Holland  by  the 
Saracens.  Venetian  lead  was  early  known  for  its  purity  and  com- 
manded a  higher  price  than  the  Dutch-manufactured  lead  on  this 

61 


62 


OLD  DUTCH  PROCESS   WHITE  LEAD. 


account.  The  establishment  of  the  white-lead  industry  in  England 
was  almost  synonymous  with  that  of  Holland,  and  evidently  was 
introduced  by  Hollanders,  hence  the  name  "Dutch  Process  Lead." 
In  this  process  thin  perforated  sheets  of  lead  are  exposed  in  gallipots 


FIG.  12. — Sheet-lead  buckles  and  pot. 

containing  a  weak  solution  of  acetic  acid  (water  with  2  J  parts  of  strong 
acid)  or  common  cider  vinegar.  The  pots  are  placed  in  long  tiers, 
each  tier  being  loosely  covered  with  boards  and  stacked  in  large  num- 
bers, 9000  to  10,000  pots  containing  60  or  more  tons  of  metallic  lead. 
The  bed  of  pots  is  then  embedded  in  tan-bark,  sawdust,  stable  litter, 
etc.,  that  ferments  and  soon  raises  the  temperature  of  the  mass  to 
140°  or  165°  F.  A  quantity  of  vinegar  containing  50  pounds  of  strong 
acid  converts  2  to  2J  tons  of  lead  into  the  carbonate  of  lead  in  about 
100  days.  The  only  attention  the  bed  requires  during  the  process  of 
corrosion  is  to  control  the  temperature  of  the  mass  by  regulating  the 
admission  of  the  air  to  the  interior  of  the  beds  by  opening  or  closing 
the  apertures  left  for  that  purpose.  The  corrosion  is  practically 
completed  at  the  end  of  60  days,  but  the  lead  is  of  light  specific  gravity, 
so  it  is  the  practice  to  allow  the  beds  to  remain  unbroken  for  30  or  40 
days  more,  in  which  time  the  lead  acquires  a  proper  density.  If  the 
lead  is  allowed  to  remain  in  the  beds  too  long,  say  5  or  6  months,  it 
is  liable  to  become  crystalline  and  transparent  and  will  be  of  poor 
covering  power.  Care  is  necessary  in  the  use  of  stable  litter  or  that 
from  flesh-eating  animals,  as  they  are  liable  to  change  the  white  car- 
bonate of  lead  as  it  forms  into  a  dark  sulphide  of  lead  from  the  sul- 
phurous hydrogen  evolved  in  the  decomposition  of  the  manure. 

At  the  time  of  stacking  the  air  in  the  bed  contains  about  20  parts 
of  oxygen ;  after  2  weeks  it  will  contain  only  17  parts ;  in  5  to  6  weeks, 
7  to  15  per  cent,  while  the  carbonic-acid  element  will  have  increased 
from  f  of  1  per  cent  to  23  or  27  per  cent  during  the  process  of  cor- 
rosion. From  30  to  40  per  cent  of  the  lead  remains  unchanged,  which 


OLD  DUTCH  PROCESS  WHITE  LEAD.  63 

is  separated  from  the  carbonate  by  passing  the  contents  of  the  pots 
through  a  series  of  rolls,  beaters,  and  screens.  The  corroded  lead  is 
then  mixed  with  water  and  ground  between  buhr-stones  to  an  impal- 
pable powder.  Generally  this  part  of  the  process  is  omitted  by  the 
quick-process  lead  manufacturers,  because  of  the  fine  state  of  divi- 
sion to  which  it  is  necessary  to  reduce  the  metallic  lead  for  these  proc- 
esses. The  uncorroded  particles  are  so  intimately  associated  with 
the  carbonate  that  they  are  indifferently  eliminated  in  the  separator, 
and  if  run  through  the  water-stones,  will  cover  the  face  of  the  stones 
with  a  coating  of  metallic  lead  that  soon  impairs  their  grinding  power 
and  imparts  a  dark  color  to  the  product. 

If  the  preliminary  washing  before  grinding  is  not  thoroughly  done 
to  free  it  from  the  acetic  acid  (which  is  a  drier)  the  powdered  carbon- 
ate will  dry  in  grains  and  lumps,  and  it  may  contain  partly  corroded 
or  pure-lead  particles,  in  which  case  the  corrosion  of  them  will  pro- 
ceed in  the  paint  coating  from  the  carbonic  acid  in  the  atmosphere. 
Added  adulterants  of  any  nature  cannot  prevent  this  secondary  cor- 
rosion. 

Silver  in  the  metallic  lead  produces  a  pinkish  cast  in  the  corroded 
lead,  while  bismuth  inclines  it  to  a  dark  or  gray  color.  Antimony, 
arsenic,  iron,  zinc,  and  other  metals  also  have  a  great  effect  on  the 
color  of  the  corroded  lead. 

After  grinding,  the  mixed  carbonate  and  water  is  mechanically 
floated  to  remove  any  coarse  particles,  then  pumped  into  large  settling- 
tanks,  where  it  is  double- washed  with  pure  soft  water  and  bicarbonate 
of  soda  in  solution  to  neutralize  any  trace  of  the  acetic  acid  that  may 
be  present.  After  giving  the  lead  time  to  settle  in  these  tanks,  the 
water  is  drawn  off,  and  the  pulp  lead,  carrying  about  24  per  cent  by 
weight  of  water,  is  pumped  to  large  shallow  copper  drying-pans  and 
the  water  evaporated.  This  drying  process  requires  from  6  to  8  days, 
the  temperature  of  the  drying-rooms  being  kept  at  from  140°  to  160° 
F.  The  lead  product  when  it  leaves  the  drying-pans  is  pulverized 
and  marketed  as  dry  white  lead  or  ground  in  buhr-stones  with 
linseed-oil  for  a  paste  or  mixed  paint. 

A  modification  of  the  Dutch  Process  Lead,  known  as  "Pulp  Proc- 
ess Lead,"  consists  of  taking  the  pulp  lead  from  the  settling-tanks 
and  placing  it  in  a  tank  of  linseed-oil  and  subjecting  the  mixture  to  a 
high-speed  mechanical  stirring  for  a  number  of  hours.  Some  of  the 
water  in  the  pulp  lead  is  expelled,  and  rises  to  the  top  of  the  mixture 
and  is  drawn  off;  but  a  great  part  of  the  24  per  cent  of  water  in  the 


64  OLD  DUTCH  PROCESS  WHITE  LEAD. 

pulp  is  mechanically  whipped  into  an  emulsion  or  forced  combina- 
tion with  the  lead.  Pulp  lead  is  decidedly  inferior;  even  if  subse- 
quently ground  it  does  not  bring  it  up  to  the  standard  grade  of  a 
white-lead  product.  Pulp  leads  are  inclined  to  chalk  more  than  the 
same  lead  submitted  to  the  full  process  of  drying,  chasing,  and  grind- 
ing. They  are  more  uncertain  in  taking  tints,  and,  when  applied  in 
frosty  weather  or  on  exposed  situations,  are  prone  to  peel.  They  also 
require  more  driers  to  aid  in  driving  off  the  surplus  water.  Their  low 
price  is  all  that  gives  them  a  market. 

By  the  "Old  Dutch  Process"  the  lead  is  neither  oxidized  nor 
carbonated  at  the  expense  of  the  acetic  acid.  The  oxygen  is  de- 
rived from  the  air,  and  the  carbonic  acid  from  the  tan-bark  or  other 
fermenting  source.  The  vapor  from  the  acid  element  as  it  is  evap- 
orated by  the  heat  of  fermentation  merely  serves  to  dissolve  the 
oxide  of  lead  as  it  forms,  converting  it  into  a  basic  acetate,  which 
is  again  decomposed  by  the  carbonic  acid,  the  acetate  being  thereby 
set  free  to  act  upon  another  portion  of  the  lead. 

This  is  shown  to  be  the  mode  of  action  by  a  modern  process  of 
corrosion,  in  which  the  protoxide  of  lead  (PbO)  is  moistened  with 
water  containing  about  1  per  cent  of  the  neutral  acetate  of  lead 
(sugar  of  lead,  PbO.C4H6O3)  and  a  current  of  carbonic-acid  gas  passed 
over  it,  the  litharge  being  quickly  converted  into  an  excellent  white 
lead. 

There  are  many  modifications  of  the  "Old  Dutch  Process"  that 
are  referred  to  hereafter ;  all  intended  to  improve  the  product,  shorten 
the  period  of  corrosion,  and  avoid  the  deleterious  effect  of  the  gases 
evolved  from  the  corroding  lead,  upon  the  workmen.  In  fact,  all 
the  operations  connected  with  the  manufacture  and  use  of  lead 
products  by  any  process,  from  the  lead  ore  to  a  pigment,  are  exceed- 
ingly detrimental  to  the  health  of  all  persons  so  engaged,  even  with 
the  best-known  precautions. 

When  honestly  and  thoroughly  done  through  the  long  chain  of 
operations  called  the  "Old  Dutch  Process,"  the  product  is  as  fine, 
smooth,  and  homogeneous  in  character  as  any  known  pigment,  and 
can  be  used  with  little  or  no  waste.  It  is  particularly  free  from 
sulphur  compounds,  which  invariably  change  lead  from  a  carbonate 
to  a  sulphide,  to  the  detriment  of  the  color  and  life  of  the  paint. 

Even  with  the  best  of  care  in  the  corrosion,  "Old  Dutch  Process" 
lead  differs  greatly  in  character.  The  product  from  the  centre  of 


OLD  DUTCH  PROCESS  AND  COMMERCIAL  WHITE  LEAD.    65 

the  stack  may  differ  from  that  at  the  side  walls,  where  more  moisture 
is  present.  An  excess  of  moisture  gives  the  grains  a  sugary  appear- 
ance. The  evenness  of  temperature  in  the  stack,  due  to  many  causes, 
also  the  time  of  the  year  that  the  corrosion  is  effected,  governs  the 
quantity  and  quality  of  the  product. 

Commercial  white  lead  is  often  inadequately  corroded,  washed, 
and  ground.  Pieces  of  uncorroded  lead,  tan-bark,  and  other  sub- 
stances from  the  ferment-packing,  are  incorporated  in  the  pigment, 
subsequent  decomposition  of  which  in  the  mixed  paste  or  paint 
discolors  it  and  shortens  the  life  of  the  paint.  To  such  an  extent 
is  the  careless  corrosion  of  lead  practised,  that  the  brand  of  "Old 
Dutch  Process"  is  called  in  derision  "the  happy-go-lucky  process" 
by  the  advocates  of  the  so-called  "  quick  process."  It  is  no  longer 
a  criterion  of  perfection  in  manufacture  and  purity,  unless  obtained 
directly  from  reputable  manufacturers  or  dealers.  Nevertheless, 
white-lead  paste  has  held  its  former  excellence  and  in  some  cases 
has  been  improved.  It  is  also  safe  to  say  that  but  few  corroders 
continued  to  use  the  Old  Dutch  Process,  however  desirable  it  may 
be  to  have  the  reputation  for  so  doing,  owing  to  the  confidence  that 
painters  and  users  of  paints  have  in  its  merits,  which  have  been 
known  and  established  for  centuries. 

Some  of  the  modern  processes  of  corrosion  consist  in  the  reduc- 
tion of  metallic  lead  into  ribbons  or  wires,  or  subjecting  the  molten 
lead  to  the  action  of  an  air  or  steam  blast,  by  which  it  is  riven  into 
small  particles,  greatly  increasing  the  surface  exposed  to  the  action 
of  the  acetic  acid,  thus  expediting  the  formation  of  the  acetate  of 
lead,  which  is  afterwards  corroded  by  passing  carbonic-acid  gas 
over  it;  the  latter  being  generated  in  special  apparatus,  or  by  the 
hot  products  of  combustion  from  gaseous  fuel.  These  processes, 
while  they  cheapen  and  hasten  the  corrosion,  have  not  improved 
the  quality  of  the  product  or  lessened  the  dangers  to  the  employes. 

The  product  by  these  latter-day  processes  is  not  only  coarser 
in  composition,  but  in  some  cases  is  decidedly  crystalline,  and  carries 
the  water  of  crystallization,  that  is  afterwards  set  free  in  the  grinding 
process,  into  the  paste  or  paint,  to  their  detriment,  and  the  surface 
they  cover,  whether  it  is  of  wood  or  metal. 

All  gaseous  fuel,  unless  purified  by  special  processes,  and  with 
great  care,  as  in  the  practice  of  purification  of  illuminating  coal- 
gas,  contains  sulphurous-acid  vapor  in  its  composition.  However 
little  of  this  substance  is  taken  up  by  the  lead  exposed  to  its 


66  QUICK-PROCESS  WHITE  LEADS. 

action,  its  detrimental  effects  will  be  seen  sooner  or  later  in  the 
product. 

The  sulphite  of  lead  (PbSO3),  prepared  by  passing  sulphurous 
oxide  into  a  solution  of  neutral  plumbic  acetate  (sugar  of  lead), 
is  a  white  insoluble,  anhydrous  powder  called  "  precipitated  white 
lead."  It  is  of  comparatively  recent  use  and  is  favorably  reported 
upon  for  a  pigment. 

The  hydrated  carbonates  of  lead,  formed  by  the  direct  action  of 
carbonic  acid  on  the  hydrate  of  lead  (Pb.(OH)2),  differs  from  the  pre- 
cipitated carbonates  in  being  amorphous  and  perfectly  opaque; 
whereas  the  precipitated  carbonate  is  an  aggregate  of  minute  trans- 
parent crystalline  grains.  Hence  the  former  are  the  best  pigments; 
their  greater  opacity  gives  what  the  painters  call  "body." 

In  the  German,  Austrian,  or  Chamber  processes  of  corrosion,  the 
lead  is  used  in  sheets  1"X8"X12",  1800  or  2000  sheets  in  a  box,  8 
boxes  to  a  chamber  that  may  contain  12  to  24  tons  of  lead.  The 
walls  of  the  chamber  are  lined  with  metal  and  heated  by  steam. 
The  carbonic-acid  gas  is  made  by  the  fermentation  of  vinegar,  yeast, 
and  other  substances,  ammonia,  phosphate  of  magnesia,  etc.,  being 
added  to  hasten  the  fermentation.  Carbonic  acid  from  burning 
charcoal  and  other  methods  are  employed  for  generating  the  car- 
bonic-acid gas  in  great  volume,  for  a  quick  corroding  vapor  to  fill 
the  chamber. 

The  Kremser  white  or  Klangenfurt,  a  German  corrosion  process, 
uses  the  vinegar  from  dried  grapes  as  an  excitant  to  corrosion.  The 
best  quality  of  this  process  lead  is  claimed  to  be  whiter  than  the 
"Old  Dutch  Process"  leads  and  to  cover  equally  as  well. 

Krem's  or  Crem's  white  is  a  poorer  quality  of  the  "Kremser 
process  "  lead. 

Kremnitz  white  is  a  product  from  Kremnitz's  (German)  dry 
precipitation  process. 

Flake-white  is  a  pure  white  lead  in  a  scaly  form  rather  than 
as  crystals  or  grains — the  usual  form  from  the  Dutch  process.  It 
lacks  opacity  or  covering  power. 

The  Clichy  or  French  process  is  the  principal  quick-corrosion 
process  used  in  France.  The  product  is  known  as  Ceruse  de  Clichy. 
It  is  entirely  different  from  the  other  decomposition  or  precipitation 
processes  mentioned  before.  The  white  lead  is  formed  by  passing 
carbonic-acid  gas  for  12  to  14  hours  through  a  sugar-of-lead  or  litharge 
and  acetic-acid  solution,  forming  a  subacetate  of  lead.  The  sediment 


QUICK-PROCESS  WHITE  LEADS.  67 

formed  is  more  or  less  crystalline,  loose  or  coarse  in  grain.  It  takes  up 
less  oil  than  the  Old  Dutch  Process  leads,  allows  more  light  to  pass 
through  it,  hence  does  not  cover  nearly  so  well. 

Greneberg's  (German)  process  consists  of  the  action  of  carbonic 
acid  on  finely  divided  lead  and  litharge  while  being  rolled  constantly 
in  tight  metallic  cylinders.  The  mechanical  friction  aids  the  corro- 
sion at  the  expense  of  the  purity  and  durability  of  the  product,  though 
there  is  less  exposure  of  the  workman  to  the  corrosion  fumes  in  this 
part  of  the  process. 

Milner's  (English)  process  produces  white  lead  in  two  days  by 
the  action  of  carbonic  acid  on  oxychloride  of  lead  (litharge)  by 
grinding  them  together  with  common  salt  in  water. 

Pattison's  (English)  lead  is  a  wet  precipitation  product — the  oxy- 
chloride of  lead,  made  by  the  action  of  muriatic  acid  on  galena  (lead 
ore). 

The  Carter  (American)  process  is  a  modification  or  an  improve- 
ment on  the  Kremnitz  (German)  process.  Metallic  lead  is  melted, 
and  while  molten  is  riven  into  fine  particles,  like  flour,  by  a  jet  of  high- 
pressure  superheated  steam.  This  amorphous  powder,  of  a  steel- 
gray  or  dark-blue  color,  is  charged  into  a  revolving  cylinder  5  to  7 
feet  in  diameter  by  8  to  12  feet  long.  One  end  of  the  cylinder  is  con- 
nected to  an  exhaust-fan  and  the  other  end  to  a  flue  leading  from  a 
furnace  where  carbonic-acid  gas  is  generated  from  burning  charcoal. 
Generally  the  products  of  combustion  from  a  coke  fire  under  the 
steam-boiler  of  the  plant  are  used  for  the  corroding  gas,  the  furnace 
gases  having  been  washed  and  purified  to  free  them  from  any  sulphur 
present.  The  temperature  of  the  revolving  cylinder  and  the  charge 
of  powdered  lead  is  kept  at  about  140°  F.  during  the  process.  Dilute 
acetic  acid  and  hot  water  are  sprayed  into  the  chamber  at  different  times 
during  the  corrosion  process,  the  stage  of  which  is  always  accessible  for 
inspection  by  removing  samples  of  the  lead  without  interrupting  the 
chemical  action  of  corrosion.  The  agitation  or  turning-over  of  the 
lead  and  its  exposure  to  the  heat  is  constant  during  the  process. 
About  95  per  cent  of  the  lead  is  changed  to  white  lead  by  this  process 
instead  of  60  to  70  per  cent  by  the  Old  Dutch  Process.  The  presence 
of  antimony,  bismuth,  silver,  zinc,  and  other  metals,  affects  the  color 
and  quality  of  the  lead  by  this  process  as  well  as  in  all  others.  The 
treatment  of  the  white-lead  powder  after  it  leaves  the  cylinder  to 
form  the  dry  white  lead  or  the  paint  paste  is  similar  to  the  Old  Dutch 
or  other  processes.  The  powder  is  repeatedly  washed  with  water  to 


68 


CARTER'S  PROCESS  WHITE  LEAD. 


free  it  from  the  acetic  acid,  ground  in  water  to  a  pulp  form,  and 
floated  through  a  number  of  tanks  and  allowed  to  settle.  The  greater 
the  care  used  to  eliminate  the  acid  the  more  reliable  will  be  the  product. 
The  products  of  all  of  the  above  processes,  as  well  as  of  many 
other  quick  processes,  vary  in  some  degree  of  quality  or  form  of  the 
white-lead  atoms  from  that  of  the  "Old  Dutch  Process."  The  latter 
can  be  said  to  rank  as  the  standard  for  purity,  fineness,  and  all  other 
qualities  which  are  indifferently  imitated  in  most  of  the  quick-process 
products,  the  Carter  being  probably  the  best  of  them. 


FIG.  13. — The  Carter  process  for  manufacturing  white  lead. 

Many  of  the  quick-process  leads  contain  acetic  and  carbonic 
acids;  the  former,  being  added  in  excess  of  the  amount  necessary 
for  a  natural  rate  of  corrosion  by  the  old  methods,  remains  in  the 
corroded  product  and  requires  a  more  thorough  washing  to  remove 
it  than  it  customarily  receives.  The  acid  element  is  often  strong 
enough  to  redden  litmus-paper,  which  would  be  discovered  if  the 
dry  white-lead  powder  could  be  obtained  to  make  the  test.  The 
acid  causes  loss  of  opacity  and  rapid  chalking.  The  corrosion  of  the 
lead  is  simply  removed  from  the  corroding  stack  to  the  paint  coat- 
ing, the  carbonic  acid  and  the  moisture  required  in  this  secondary 
process  are  both  present  in  the  atmosphere,  and  not  only  the  carbonate 


QUICK-PROCESS  WHITE  LEADS.  69 

of  lead  is  formed,  but  this  is  further  reduced  to  a  subcarbonate  of 
lead;  the  latter  change  constitutes  the  chalking  stage  in  the  decay 
of  the  coating.  Acetic  acid  and  uncorroded  lead,  left  by  imperfect 
washing  and  grinding,  are  frequently  present  in  commercial  white 
leads.  Ten  per  cent  of  lead  acetate  is  often  found  in  the  "  flake- 
whites."  Most  of  the  quick-process  or  impure  leads  come  to  the 
market  in  some  form  of  " whites"  with  a  misleading  trade-mark. 

The  report  of  the  Committee  of  Experts  appointed  by  the  English 
Home  Secretary  to  investigate  the  manufacture  of  lead  products,  as 
to  the  character  and  quality  of  the  product,  also  their  effect  upon  the 
health  of  the  workmen,  was:  That  they  visited  forty-six  establish- 
ments using  various  processes  for  manufacturing  white-lead  pigments, 
all  of  which  were  dangerous  to  the  health  of  persons  so  employed, 
and  while  some  of  the  substitute  leads  were  cheaper  to  make,  and 
possibly  a  little  less  injurious  to  the  workmen^  their  products  were 
far  from  equalling  in  quality  those  from  the  "Old  Dutch  Process," 
and  they  could  not  recommend  either  the  processes  or  products  as 
against  the  "Old  Dutch  Process  "  leads. 

Baryta  white  is  prepared  from  the  native  sulphate  of  barium,  or 
from  the  carbonate  of  baryta,  artificially  treated  with  sulphuric 
acid.  (See  Barytes,  Inert  Pigments,  Chapter  XVIII.) 

Krem's,  Nottingham,  and  Newcastle  whites  are  pure  white  leads 
differing  only  in  the  process  by  which  they  are  made.  Hamburg, 
Holland,  and  many  foreign-made  whites  contain  from  3  to  60  per 
cent  of  barytes  and  chalk,  and  are  adulterated  compounds  of  white 
lead.  Venice  white  generally  consists  of  equal  parts  of  white  lead 
and  barytes.  All  pastes  and  mixed  paints  classified  and  marketed 
as  "whites"  are  usually  only  adulterations  of  white  lead,  and  no 
responsible  and  honest  corroders  of  white  lead  ever  so  denominate 
their  products.  The  name  "white,"  whatever  its  trade  prefix, 
should  usually  be  viewed  with  suspicion  of  its  quality.  (See  tests  of 
white  lead  on  the  following  pages.) 

About  110,000  tons  of  metallic  lead  are  annually  corroded  to 
white  lead,  in  the  United  States,  by  the  various  processes,  or  about 
one-third  of  the  total  production  of  the  metal  product. 

There  are  twenty-two  manufacturers  using  the  "Old  Dutch 
Process"  in  the  United  States,  and  five  using  the  "Quick  Process." 

The  first  white  lead  corroded  in  the  United  States  was  by  Samuel 
Wetherell  in  1810  at  Philadelphia,  followed  by  Christian  Bielen  in 


70  ELECTROLYTIC  WHITE  LEAD. 

1811  at  Pittsburg.     Cincinnati  also  had  a  white-lead  plant  shortly 
afterward. 

Electrolytic  White  Lead* 

This  process  is  a  radical  departure  from  all  of  the  other  processes 
for  producing  white  lead,  in  not  employing  acetic  acid,  but  by  acting 
upon  the  lead  in  the  form  of  pigs  with  nitric  acid,  which  is  generated 
by  electricity.  The  process  consists  of  four  consecutive  steps: 

First  The  electrical  preparation  of  nitric  acid  and  sodium  hy- 
droxide. 

Second.  The  action  of  the  nitric  acid  on  the  metallic  lead  form- 
ing lead  nitrate,  Pb(NO2)2+H2. 

Third.  The  reaction  of  lead  nitrate  and  sodium  hydrate  to  form 
lead  hydroxide,  viz.:  Pb(NO2)2+2NaOH==Pb(OH)2+2NaNO3. 

Fourth.  The  combination  of  the  lead  hydroxide  and  sodium  bicar- 
bonate to  form  lead  carbonate,  Pb(OH)2+HNaCO3  +  NaOH+H2O. 

Reactions  2  and  3  may  not  take  place  strictly  as  given,  which 
are  the  theoretical  combinations,  but  some  approximate  reactions 
are  had,  for  the  extra  hydrogen  present  is  liberated  at  the  electrode. 

The  chemical  operations  in  the  process  are  briefly: 

First,  a  solution  of  nitrate  of  sodium  (NaN03)  is  decomposed 
by  .an  electric  current  from  a  dynamo,  the  strength  of  the  solution 
not  being  important — 10°  Baume"  or  one  pound  per  gallon  suffices. 
This  solution  is  put  in  a  series  of  wooden  cells  divided  into  two  com- 
partments by  porous  partitions.  At  the  positive  electrode  is  fastened 
a  pig  of  lead,  at  the  negative  a  sheet  of  copper.  On  applying  the 
current  the  nitrate  of  sodium  is  decomposed  according  to  the  equa- 
tion 1  given,  nitric  acid  collecting  at  the  positive  electrode  and 
sodium  hydroxide  at  the  negative.  The  nitric  acid  at  once  attacks 
the  lead  and  forms  lead  nitrate,  which  dissolves  (equation  2) 
the  hydrate  of  sodium,  producing  no  effect  upon  the  copper  at  the 
negative  pole. 

Finally,  both  solutions  are  separately  drawn  off  and  mixed,  as 
desired,  in  quantitative  proportions  in  any  suitable  vessel.  The  result, 
as  shown  in  equation  3,  gives  the  lead  hydroxide  as  a  white 
amorphous  precipitate  and  leaves  the  nitrate  of  sodium  in  solution. 

*  "Electrolytic  process  for  the  manufacture  of  white  lead."  A  paper  read 
before  the  American  Chemical  Society  by  E.  P.Williams.  Reprinted  in  Elec- 
trical World,  Sept.  14,  1895,  pp.  289-90.  Mr.  Arthur  G.  Brown,  Inventor,  1892. 


ELECTROLYTIC  WHITE  LEAD.  71 

This  is  practically  the  original  nitrate,  and  can  be  used  over  and  over 
again  as  the  source  for  more  nitric  acid.  The  loss  of  the  sodium  is 
small,  and  a  little  additional  fresh  sodium  hydrate  restores  its  strength. 

The  lead-hydrate  precipitate  (Pb(OH)2)  is  then  filtered  from  the 
sodium  hydrate  by  a  rotary  separator,  and  the  nitrate  of  sodium 
returned  to  the  original  reservoir. 

The  fourth  step  is  in  some  respects  the  most  interesting  of  all, 
and  consists  in  adding  to  the  lead  hydroxide  a  solution  of  bicar- 
bonate of  soda  (or  the  normal  carbonate).  Reaction  4  at  once  takes 
place.  It  will  be  noticed  that  the  sodium  hydroxide  is  the  product 
in  solution,  and  lead  carbonate  the  precipitate. 

The  sodium  hydroxide  removes  most  of  the  impurities,  if  there 
are  any,  in  the  hydrate  of  lead.  It  dissolves  any  salts  of  alumina 
or  zinc  present,  and  it  removes  the  organic  matter.  These  impurities 
appear  in  the  solution,  leaving  the  precipitated  lead  remarkably  fine 
and  white.  The  hydroxide  of  sodium  is  again  converted  into  bi- 
carbonate by  passing  carbonic  acid  into  it,  and  this  is  used  again. 
Thus  the  main  agents  in  each  of  the  two  principal  steps,  the  nitrate 
of  sodium  and  the  bicarbonate  of  sodium,  are  made  to  do  duty  over 
and  over  again  with  but  slight  additions  to  restore  the  strength. 

The  use  of  free  nitric  acid  in  the  process  is  objectionable,  as  under 
the  influence  of  electricity  it  breaks  up  with  intolerable  fumes;  also 
for  other  reasons.  Acetic  acid  is  also  objectionable  for  the  same 
reasons,  hence  the  recourse  to  sodium  or  potassium  nitrates  for  the 
reactions. 

The  cost  of  white  lead  by  this  process  is  but  a  fraction  of  that 
by  the  "Old  Dutch  Process,"  as  the  lead  is  used  as  it  comes  from  the 
smelting-furnace  in  pigs  and  requires  no  remelting  or  casting  into 
buckles  or  shreds,  as  in  the  corrosion  processes,  and  the  whole  process 
is  complete  in  a  day,  or,  for  that  matter,  in  an  hour,  as  all  of  the  re- 
actions take  place  rapidly,  if  not  instantaneously,  no  free  acids  are 
used,  and  the  sodium  compounds  are  recovered,  as  noted. 

The  texture  of  the  lead  product  is  almost  molecular  in  fineness 
and  does  not  require  grinding,  it  being  so  fine  that  it  remains  sus- 
pended in  the  water  for  a  long  time,  and  in  order  to  filter  it  a  special 
brand  of  cloth  is  used,  as  filter-paper  would  scarcely  retain  it. 

Its  covering  power  applied  side  by  side  with  the  Dutch  Process 
lead  appears  to  be  equal  to  it,  possibly  a  little  better,  but  never  found 
to  be  less. 

Whether  the  electrolytic  lead  will  displace  the  "Old  Dutch  Process ". 


72  ELECTROLYTIC  WHITE  LEAD. 

lead  to  any  great  extent  remains  for  time  to  determine.  The  French 
or  Clichy  process  lead,  or  "Clichy  white/'  was  thought  at  first  to  be  a 
revolutionary  one,  but  the  product  finally  proved  to  be  decidedly 
inferior  to  the  Dutch  Process1  lead,  from  its  crystalline  character. 
It  does  not  give  the  opacity  or  body,  or  spread  as  well  under  the  brush, 
or  cover  as  much  surface  as  the  Dutch  Process  lead. 

The  "  Dutch  Process  "  lead  forms  a  globular  atom,  viz. :  two  atoms 
of  the  carbonate,  PbCO3,  and  one  atom  of  the  hydrate  of  lead, 
Pb(OH)27  but  this  composition  does  not  always  appear  to  be  of  con- 
stant quality,  as  much  depends  upon  the  care  given  during  the  corrosion 
part  of  the  process. 

Lead  hydrate,  or  the  hydrate  oxide,  is  a  white  amorphous  sub- 
stance. The  carbonate  may  be  either  globular  or  crystalline,  depend- 
ing upon  the  methods  of  its  preparation.  Now,  certain  qualities 
of  these  two  forms  are  quite  unlike,  and  this  explains  why  the  use 
of  one  has  continued  and  the  other  been  abandoned  as  a  pigment. 
The  atoms  of  the  one  form  are  said  to  be  from  ^-^  to  Tofoiy  incn  m 
diameter,  and  in  the  grinding  with  the  oil  take  it  up  somewhat  as  a 
sponge  absorbs  water.  In  the  "  Dutch  Process  "  leads,  when  properly 
corroded,  the  atoms  are  globular,  and  to  this  is  due  the  greater  body 
and  permanency  of  the  paint  over  that  from  any  of  the  quick-process 
leads.  The  crystalline  form  does  not  absorb  near  the  same  amount 
of  oil,  no  matter  how  finely  it  may  be  ground,  as  the  surface  of  the 
crystals,  either  whole,  as  formed,  or  crushed  in  the  grinding,  are  im- 
pervious and  do  not  have  the  same  light-dispersing  or  reflecting  power. 
Hence  their  poor  covering  quality;  and  they  do  not  bond  to  or  in  the 
vehicle  as  well — they  save  oil. 

If  by  the  electrolytic  process  it  is  possible  (as  it  is  claimed)  to 
produce  a  pure  carbonate  of  lead,  or  a  mixture  of  the  carbonate 
and  hydrate  of  lead  in  any  proportion  required,  and  the  product 
proves  to  be  fine  and  globular  instead  of  coarse,  granular,  or  crystalline, 
there  should  be  no  doubt  regarding  its  merits,  but  the  few  hundred 
tons  thus  far  spread  do  not  afford  sufficient  data  for  a  wholesale 
abandonment  of  the  "  Old  Dutch  Process "  with  its  centuries  of 
established  reputation. 

Mr.  E.  Bailey,  York,  England,*  has  invented  a  so-called  electrical 

process  for  the  manufacture  of  white  lead  and  other  metallic-oxide 

compounds.     An  electric  arc  keeps  the  lead  in  a  molten  state.     The 

melted  lead  is  then  acted  upon  by  gaseous  vapors  blown  through  it 

*  London  Electrical  Engineer,  Jan.,  1901. 


ELECTROLYTIC  WHITE  LEAD.  73 

to  produce  the  carbonate  or  oxide  of  lead.  The  fumes  produced 
are  blown  into  chambers  having  canvas  or  fine-fabric  cloth  covers 
or  roofs.  The  fine  powders  fall  down  and  are  collected  for  pigments, 
and  require  no  washing.  The  uncondensed  vapors  escape  through 
the  cloth  screens  to  the  atmosphere  or  stack.  A  saving  of  50  per  cent 
is  claimed  for  the  process  over  that  of  the  "  Old  Dutch  Process,"  but 
like  all  other  quick-process  leads,  the  merits  of  the  product  are  yet 
to  be  established.  , 

There  never  has  been  any  difficulty  in  quickly  corroding  or  oxi- 
dizing metallic  lead  or  zinc  for  use  as  a  pigment.  The  difficulty  with 
all  quick-process  leads  is  in  the  quality  of  the  product,  and,  though  the 
processes  are  patented  from  Dan  to  Beersheba,  the  ornate  devices  and 
claims  of  the  patent-office  document  do  not  put  the  wearing  and 
other  desirable  qualities  into  the  product  that  the  patent  claims  allege 
to  be  there. 

There  is  nothing  electrolytic  in  the  Bailey  process.  The  melting 
of  the  lead  by  an  electric  current  previous  to  or  during  the  action  of 
the  corroding  gases  produces  no  electrolysis  in  the  molten  metal,  the 
heating  of  which  could  be  as  readily  and  more  cheaply  done  by  a  coal 
or  other  fire.  The  collection  of  the  metallic  vapors  by  screens  is  an 
old  method  of  pigment  manufacture — in  use  for  the  production  of 
sublimated  lead,  as  described  in  Chapter  VI,  and  is  void  of  electro- 
lytic action. 


CHAPTER  VI. 


WHAT  CONSTITUTES  A  GOOD  WHITE  LEAD. 

MULDER'S  and  Phillips's  analyses  determined  that  there  are  three 
varieties  of  white  lead  in  the  best  classes  of  that  product  experimented 
with  under  the  general  formula  of  the  hydrated  carbonate,  PbCO3,  viz. : 
2Pb"C03.  Pb"H2O2;  5Pb"C03,3Pb"H2O2;  3Pb"CO3.  H2O2. 

A  properly  corroded  white  lead  should  contain  oxide  of  lead  com- 
bined with  water — water  lead  (hydrate  of  lead,  Pb(OH)2.),  from  25  to 
32  per  cent,  which  in  its  effect  upon  the  vehicle  is  similar  to  red  lead ;  it 
absorbs  oxygen  and  hardens  the  coating  by  converting  a  part  of  the 
oil  into  a  soap  that  has  no  covering  power  whatever.  The  other  75 
to  68  per  cent  should  be  oxide  of  lead  combined  with  carbonic  acid 
(carbonic-acid  lead),  that  really  injures  the  oil  in  the  paint,  but  gives 
all  of  the  covering  properties  that  the  paint  possesses.  The  chalking 
of  white-lead  paint  is  due  to  this  75  per  cent  of  carbonic-acid  lead. 
A  paint  composed  wholly  of  carbonic-acid  lead  will,  in  a  short  time, 
chalk  as  freely  as  a  whitewash.  The  carbonic-acid  lead  gives  the 
whiteness  or  color,  the  water  lead,  the  hardness  or  durability  to  the 
coating. 

In  the  following  table  from  Heiss's  experiments, 

Number  1  is  a  good  dense  white  lead.     Specific  gravity,  6 . 32 
"      2    "    dry  white  lead.  "  "6.50 

"      3    "    crystalline  transparent  lead.  "  "         6.05 


Number  1. 

Number  2. 

Numbers. 

Oxide  of  lead  .             .    . 

85  95  per  cent 

86  18  per  cent 

83  53  per  cent 

Carbonic  acid  

11  14     "      " 

10  44     "      " 

15  70     "      " 

Combined  water  

2.91     "      " 

3.38     "      " 

0  77     "      " 

Another  comparative  table  is: 


White  lead,  best  quality.  . 
"      2d         "       .. 

"         "      3d         " 

Residue  lead 

Improperly     corroded     o 

useless  lead.  . 


Lead. 


86 . 80  per  cent. 
86.24  "   " 
86.03  "   " 
84.69  "   " 

83.47  "   " 


Carbonic  Acid.          Combined  Water. 


11. 16  per  cent. 
11.68     "      " 
12.28     "      " 
14.10     "      " 

16.15     "      " 


2.00  percent. 
1.81     "      " 
1.68     "      " 
0 . 93     "      " 


0.25 


74 


WHAT   CONSTITUTES  A   GOOD   WHITE  LEAD. 


75 


In  Prof.  Hurst's  analyses  of  four  samples  of  "Old  Dutch  Process" 
white  lead,  the  carbonate  ranged  from  65.35  to  72.15  per  cent,  the 
hydrate  from  25.19  to  36.14  per  cent,  and  the  moisture  0.42  per  cent 
to  nil. 

Mr.  Converse's  analyses  of  five  samples  of  the  best  brands  of 
American  "Old  Dutch  Process"  leads  gave 


Lead  carbonate  

85  32 

79  37 

78  58 

77  Q8 

fiQ  Qfi 

"    hydrate  

14  83 

19  80 

20  11 

20  fiO 

on  in 

"    oxide  

1  48 

1  48 

Water 

0  03 

0  21 

0  07 

A  very  hard  white  lead  that  contains  no  water  lead  will  not  harden 
when  spread,  but  brush  off  like  a  lime  whitewash.  When  this  occurs 
where  the  necessary  amount  of  oil  has  been  used,  the  painter  can  be 
quite  sure  that  the  lead  is  a  poorly  corroded  or  quick-process  lead,  or 
a  synthetically  formed  lead  from  an  acid-solution  process.  Carbon- 
ate of  lime  (chalk,  whiting),  gypsum,  and  other  so-called  inert  sub- 
stances added  to  such  a  lead  do  not  correct  this  chalking;  they  only 
disguise  it  for  the  time  being,  and  increase  the  tendency  of  such  lead 
paints  to  turn  yellow  and  lessen  their  covering  power. 

All  white  lead  on  external  exposures  is  liable  to  chalk,  because  it 
contains  too  much  carbonic-acid  lead  as  it  comes  from  the  manufac- 
turer, or  has  taken  another  portion  of  carbonic  acid  from  the  atmos- 
phere at  the  expense  of  the  water  lead,  and  formed  a  subcarbonate  of 
lead  (the  chalk  product,  PbCO2),  or  has  too  little  oil  in  it  when  spread, 
or  has  not  been  well  ground  in  the  oil.  Paints  thus  affected,  if  brushed 
over  with  a  coating  of  white  lead  ground  with  an  excess  of  oil,  will  prove 
to  be  more  durable  and  less  affected  by  future  chalking  than  the 
original  coating,  or  a  new  heavy  coat  from  the  same  lead. 

The  formation  of  a  lead  soap  in  the  ordinary  process  of  grinding 
and  mixing  white-lead  pastes  or  paints  is  a  disputed  point  by  paint 
chemists.  But  the  lead  hydroxide  and  the  free  linoleic  acid  in  linseed- 
oil,  if  acetic  acid  is  present  in  the  white  lead,  will  combine  and  form  a 
lead-soap  mixture.  The  paint  containing  this  soap,  on  exposure  to 
the  weather,  soon  loses  its  lustre  and  will  crumble  or  chalk. 

The  presence  of  lead  soap  in  many,  if  not  the  most,  of  white-lead 
paints  is  shown  by  Prof.  Church,  in  his  "Chemistry  of  Paints  and 
Painting,"  as  follows:  "Upon  a  piece  of  glass  place  a  small  quantity 
of  the  white-lead  paint,  and  add  a  10  per  cent  solution  of  sulphuric 
acid.  Work  the  mixture  together  with  a  glass  rod  or  spatula  into  a 


76  CHAIRING  OF  WHITE  LEAD. 

cream-like  condition.  The  acid  will  soon  destroy  the  oily  or  hydro- 
fuse  character  of  the  paint.  With  zinc  white  or  baryta  white  in  oil 
no  such  admixture  is-  possible,  for  in  these  paints  the  oil  will  not 
saponify  owing  to  the  absence  of  an  acid." 

Mulder's  and  other  experiments  proved  that  the  chalking  of  white 
lead  was  due  solely  to  the  absence  of  water  lead  in  the  pigment,  unless 
the  lead  was  badly  adulterated,  in  which  case  this  effect  was  directly 
traceable  to  the  adulterant  used. 

In  general,  all  the  latter-day-process  white  leads  are  more  inclined 
to  chalk  than  the  "Dutch  Process"  leads.  This  arises  (as  stated 
before)  from  the  smaller  amount  of  water  lead  in  their  composition, 
and  being  of  a  crystalline  instead  of  a  globular  form.  In  the  grinding 
process  these  crystals  or  grains  are  broken  down,  and  the  combined 
or  formative  water  necessary  for  their  existence  in  the  form  of  crystals 
is  dispersed,  rendering  the  broken  lead  atoms  more  sensitive  to  the 
attack  of  the  atmospheric  carbonic-acid  element,  that  finds  in  their 
sharp  angular  form  a  more  favorable  surface  to  act  upon.  Only  a 
comparatively  slight  action  of  the  carbonic  acid  on  the  freshly  crushed 
atoms  of  the  lead  is  required  to  change  it  to  the  subcarbonate,  and 
leave  it  free  to  be  brushed  off  by  friction  or  washed  out  by  storms. 

Old  white  lead,  or  that  which  has  been  ground  in  oil  to  a  paste  for 
a  year  or  more,  chalks  decidedly  less  than  recently  corroded  lead, 
by  whatever  process  it  is  made.  The  atoms  of  the  pigment  in  the  case 
of  old  lead  have  had  time  to  release  themselves  from  the  tension  due 
to  their  formation  and  grinding.  Adulterations  do  not  prevent  these 
inexorable  chemical  changes  in  the  lead  pigment;  they  only  increase 
the  disintegrating  action. 

If  oxide  of  zinc  is  used  to  give  hardness  in  place  of  the  water  lead 
in  paints  exposed  in  open  air,  the  atmospheric  moisture  and  carbonic 
acid  changes  the  oxide  of  zinc  (ZnO)  to  a  zinc  carbonate  (ZnCO3) 
whose  volume  is  nearly  double  that  of  the  oxide  from  which  it  was 
formed  in  the  hardened  paint,  and  peeling  takes  place  instead  of 
chalking.  The  cheaper  forms  of  zinc  oxide  contain  zinc  sulphite, 
which  blackens  the  paint  and  otherwise  injures  the  coating. 

If  gypsum,  barytes,  or  silica  are  used  for  the  adulteration,  they 
lack  both  in  covering  and  light-dispersing  (coloring)  power,  and,  from 
their  sharp,  angular,  or  irregular  form  as  pigment-atoms,  do  not  bond 
themselves  in  the  oil,  for  which  they  have  no  affinity,  nor  enter  into 
combination  with,  or  bond  to  the  covered  surface.  They  prevent 
chalking  only  as  their  presence  leaves  less  white  lead  to  chalk,  even 


CHALKING  OF   WHITE  LEAD. 


77 


if  they  do  not  actually  increase  its  tendency  towards  that  change,  as 
the  sharp,  rough  surface  of  the  paint  containing  these  adulterants 
holds  the  atmospheric  moisture  and  gases  closer  and  longer  for  their 
action.  (See  Decay  of  Paint  and  Inert  Pigments,  Chapter  XXVII.) 

White  lead  unites  thoroughly  with  the  oil.  Zinc  white  combines, 
but  very  slowly ;  barytes  does  not  combine  at  all.  All  pigments  that 
contain  crystals  or  are  granular  are  deficient  in  the  light-dispersing 
power,  even  if  they  have  the  spreading  quality.  The  granular  char- 
acter of  quick-process  white  lead  is  its  great  weakness. 


LEAD 


FIG.  14. — Effects  of  sulphurous  gases  on  white  lead. 

Background  in  zinc  white.  Background  in  white  lead. 

Lettering  in  white  lead.  Lettering  in  zinc  white. 

The  quality  of  the  vehicle  has  much  to  do  with  chalking  and  the 
decay  of  white  lead.  A  good  linseed-oil  will  better  preserve  a  poor, 
or  an  adulterated  white  lead,  than  a  poor  oil  could  the  best  of  white 
lead. 

Pure  white  lead  is  soluble  in  dilute  nitric  acid.  A  sample  treated 
with  this  reagent  should  pass  entirely  into  solution,  leaving  no  residue. 
If  the  sample  is  in  the  form  of  a  paste  or  paint  the  oil  can  be  removed 
by  washing  it  with  benzine  or  ether,  and  the  powder,  when  dried  upon 
blotting-paper,  should  leave  no  stain. 

The  action  of  sulphuretted  hydrogen  upon  white  lead  is  that  the 
sulphur  element  unites  with  the  lead  to  form  the  sulphide  of  lead  (PbS), 
which  is  a  dark  color.  Further  exposure  changes  the  sulphide  to  a 


78  ADULTERATION  OF  WHITE  LEAD. 

sulphate  (PbS03),  which  is  white  and  of  good  covering  power.  Hence 
the  full  change  would  not  be  detrimental  to  the  coating  in  point  of 
color  were  not  these  changes  in  the  dried  coating  attended  by  a  change 
in  the  volume  of  the  lead-atoms  at  each  step  in  their  progress  from  a 
carbonate  to  a  sulphate  that  ensures  a  forced  disintegration  of  the 
coatings.  (See  Decay  of  Paint,  Chapter  XXVII.) 

The  cause  of  white-lead  paint,  when  spread  over  darker  colors, 
deteriorating  after  a  short  period  and  showing  dark,  is  not  alone 
owing  to  the  changes  mentioned  above,  but  also  that  the  fatty  acids 
in  the  oil  gradually  expel  the  carbonic  acid  in  the  lead-atoms  and  form 
a  clear  lead  soap,  through  which  the  darker  colors  beneath  show. 


Adulteration  of  White  Lead. 

The  adulteration  of  white  lead  under  the  forms  of  a  paste  or 
mixed  paint  has  reached  a  point  where  the  multitudinous  trade- 
marks under  which  they  are  marketed  are  positively  of  no  value 
to  determine  their  quality;  the  only  safety  lies  in  purchasing  from 
responsible  business  firms  of  national  reputation  for  the  standard 
quality  of  their  products  and  business  methods. 

A  late  examination  of  commercial  white-lead  pastes  purchased 
in  the  open  market  resulted  as  follows: 

Seventy-five  different  white-lead  pastes,  under  29  different  trade- 
marks and  symbols,  embellished  with  14  qualifying  adjectives,  and 
made  by  17  different  manufacturers,  plus  1  unknown  firm  that 
furnished  14  different  brands,  were  analyzed  by  16  different  analysts. 
The  condensed  results  are,  viz.: 

Sixteen  had  no  white  lead  in  their  composition,  but  were  mixtures 
of  barytes,  silica,  gypsum,  zinc  oxide,  or  whiting  in  some  proportion 
of  three  or  more  of  these  substances. 

Fifty-nine  of  the  samples  had  white  lead  from  1.24  per  cent  to 
47.62  per  cent,  and  averaged  for  all  23.35  per  cent  of  lead. 

Seventy  of  the  samples  had  barytes  from  15.60  per  cent  to  86.37 
per  cent,  and  averaged  for  all  49.61  per  cent.  One  or  more  of  the 
above  adulterants  was  used  with  white  lead  of  uncertain  quality  for 
the  balance  of  the  paste. 

In  5  of  the  samples  silica  replaced  the  barytes,  otherwise  the 
usual  group  was  unbroken. 

Seventy-five  of  the  samples  had  oxide  of  zinc  from  59.20  to 
3.60  per  cent,  averaging  for  all  27.48  per  cent.  A  free  use  of  gypsum 


ADULTERATION  OF  WHITE  LEAD.  79 

and  whiting  aided  the  white  lead  to  give  the  paste  a  semblance  of  a 
pure  white-lead  product. 

Thirty-two  of  the  samples  had  sulphate  of  zinc  in  the  paste  from 
84.85  to  0.88  per  cent,  averaging  for  all  22.09  per  cent. 

Five  samples  had  chalk  from  24.30  to  0.85  per  cent,  averaging  for 
all  9.60  per  cent. 

Wherever  carbonate  or  sulphate  of  lime  was  used  it  was  at  the 
expense  of  the  white  lead. 

The  adulteration  of  all  of  the  brands,  other  than  the  16  that  had 
no  white  lead,  ranged  from  99  to  44  per  cent,  and  averaged  for  the 
59  pastes  80.4  per  cent. 

In  5  of  the  samples  oxide  of  zinc  was  mentioned  as  constituting 
a  small  part  of  the  paste,  but  nothing  was  said  about  the  30  to  40 
per  cent  of  barytes  in  their  composition,  or  of  a  like  amount  of  the 
other  adulterants,  or  the  small  amount  of  white  lead. 

One  sample  had  a  notice  that  $1000  would  be  paid  if  the  white 
lead  in  it  was  not  pure.  It  had  no  white  lead  in  it. 

One  sample  offered  $100,  same  conditions  as  above.  It  was  of 
the  same  character.  No  white  lead  in  it. 

One  sample  had  a  $250  penalty  for  any  imitation  of  the  lead  in  it, 
or  of  the  label  on  the  package.  It  had  99  per  cent  of  adulterants. 
Possibly  a  piece  of  the  label  might  have  fallen  into  the  paste  before 
analysis  of  it. 

Probably  the  above  adulteration  record  represents  the  larger  num- 
ber of  commercial  white-lead  and  tinted-color  paints  in  the  market. 
Unfortunately,  most  of  them  get  juggled  off,  and  generally  at  the 
price  of  really  first-class  paints;  but  so  many  people  are  willing  to 
be  humbugged  to  save  a  few  cents  on  a  pot  of  paint  that  it  may  be 
a  mistake  to  enlighten  them  on  the  subject.  What  the  character  and 
quality  of  the  oils  are  that  form  an  essential  part  of  all  these  adul- 
terated and  misleadingly  named  compounds,  one  can  readily  imagine. 
Surely  they  are  equally  deceptive  and  uneliable. 

Maize-oil  is  used  frequently  to  the  amount  of  25  per  cent  in  the 
grinding  of  paint  pastes  and  paints  to  prevent  them  from  settling 
in  the  package.  It  is  a  non-siccative  oil,  and  while  not  exerting  any 
materially  bad  influence  in  a  paint,  its  use  with  linseed-oil  in  any 
quantity  can  only  be  considered  as  an  adulterant.  Its  cost  is  about 
one-half  that  of  commercial  linseed-oil.  Its  use  requires  more  driers. 

The  use  of  10  to  15  per  cent  of  barytes  in  a  white-lead  paint  may 
not  be  particularly  objectionable  in  point  of  durability,  if  the  lessened 


80  WHITE  LEAD  AND  ZINC  PAINTS. 

cost  is  the  object  desired.  Lead  pigments  do  not  cover  so  well  with 
barytes,  but  zinc  oxide  covers  better;  barytes  gives  weight  that  the 
zinc  is  deficient  in.  Some  master  painters  advocate  the  use  of  barytes 
for  the  reason  that  it  brightens  dark  colors  and  saves  oil;  but  ignore 
the  fact  of  its  darkening  light  colors,  also  its  tendency  to  yellow  them 
from  the  sulphur  element  in  its  composition  and  its  general  deficiency 
in  covering  power.  The  advantages  in  any  case  do  not  warrant  the 
use  of  from  50  to  80  per  cent  of  this  or  any  other  substance  which  does 
not  unite  with  the  oil,  and  of  themselves  are  unfit  for  a  paint.  As  a 
rule,  no  responsible  paint  firms  will  offer  such  paints  under  their  own 
names. 

Zinc  oxide  is  often  mixed  with  white  lead  for  other  than  adultera- 
tion purposes.  It  is  added  to  correct  the  tendency  of  pure  white 
lead  to  turn  yellow  from  the  action  of  sulphurous  fumes  in  the  at- 
mosphere. It  makes  the  paint  harder,  and  possibly  prevents  "  chalk- 
ing" to  some  extent,  as  there  is  not  so  much  lead  to  chalk,  but  adds  a 
tendency  to  peel  on  outside  exposures — a  result  worse  than  chalking. 
It  is  difficult  to  get  a  homogeneous  blending  of  the  two  pigments  so 
individually  unlike  in  character,  owing  to  their  different  processes 
of  formation.  Their  mechanical  association  is  far  unlike  that  of  a, 
neutral  whole,  even  with  the  best  of  supervising  care  in  blending  them. 

Many  of  the  difficulties  in  mixtures  of  white  lead  and  zinc  oxide 
are  overcome  by  the  use  of  a  natural  admixture  of  the  lead  and  zinc 
in  the  form  of  a  pigment  known  as  sublimed  lead  or  white  paint, 
hereafter  described. 

White  Lead  vs.  Zinc  Paints. 

Mr.  G.  R.  Henderson,  of  the  Norfolk  and  Western  Railroad, 
reports  a  series  of  exposure  tests  to  determine  the  efficiency  of  lead 
and  zinc  paints.  For  the  different  materials  he  reaches  the  following 
results : 

"  Tin.  The  best  results  were  obtained  with  the  first  coat  of  white 
lead  and  second  coat  of  white  zinc.  The  second  coating  of  zinc  gave 
generally  the  best  results,  and  the  second  coating  of  lead  the  worst. 

"  Galvanized  Iron.  The  same  remarks  apply  to  galvanized  iron 
that  are  given  for  tin. 

"Sheet  Iron.  The  mixture  of  one-third  white  zinc  and  two-thirds 
white  lead,  for  both  coats,  gave  the  best  results  on  this  material,  and 
in  general  the  zinc  paints  gave  better  results  than  the  lead  paints. 

"Poplar.     The  second  coats  of  zinc  showed  up  well  on  poplar,  no 


TESTS  FOR  WHITE  LEAD.  81 

matter  whether  the  priming  coats  were  white  lead  or  white  zinc  or 
mixed  lead  and  zinc.  The  lead  second  coating  showed  up  the  worst  on 
this  material,  but  in  each  case  where  the  second  coat  was  of  zinc, 
totally  or  partially,  the  paint  was  in  a  perfect  condition. 

"  White  Pine.  The  remarks  made  relating  to  poplar  apply  to  white 
pine  also. 

"  Yellow  Pine.  This  material  seems  to  be  difficult  to  properly  treat 
with  paints;  the  best  results  were  obtained  with  the  first  coat  of  lead, 
and  the  second  coat  of  lead  and  zinc  mixed.  Where  the  first  coat  was 
of  lead  and  zinc  mixed,  or  entirely  of  zinc,  the  results  were  poor 
throughout,  which  seems  to  indicate  that  as  a  general  thing  the  lead 
is  better  for  priming  on  this  material. 

"  Conclusion.  The  lead  priming  and  zinc  coating  is  generally  good 
for  tin,  galvanized  iron,  poplar,  and  white  pine.  Sheet  iron  showed 
up  best  with  both  coats  of  mixed  paints.  Yellow  pine  appeared  best 
with  the  first  coat  of  lead  and  the  second  coat  of  lead  and  zinc  mixed. 
Comparing  the  materials  which  were  painted,  we  find  that  generally 
poplar  retains  the  paint  better  than  white  pine,  and  would,  therefore, 
be  preferred  for  siding  on  buildings,  etc.  Yellow  pine  seems  to  be 
the  worst  of  all  for  this  purpose.  Black  iron,  as  a  whole,  seems  to 
retain  the  paint  better  than  either  tin  or  galvanized  iron." 

Tests  for  White  Lead. 

There  are  many  tests  for  the  purity  of  white  lead,  a  simple  one 
being  to  put  a  globule  of  the  paste  or  dry  powder  in  a  cavity  formed 
in  a  piece  of  charcoal,  and  expose  it  to  the  heat  of  a  common  blow- 
pipe, readily  extemporized  in  any  shop.  If  even  10  per  cent  of  adul- 
terants are  present  it  will  not  be  possible  to  melt  the  mass. 

White  lead  is  tested  for  barytes  by  dilute  nitric  acid,  in  which 
barytes  is  insoluble,  while  the  white  lead  passes  completely  into  the 
solution.  Whiting  and  chalk  are  detected  by  the  nitrate  solution 
yielding  a  white  precipitate  with  oxalic  or  sulphuric  acid  or  oxalate 
of  ammonia,  after  having  been  treated  with  sulphuretted  hydrogen  or 
a  hydrosulphuret  to  throw  down  the  lead. 

White  lead  dissolves  with  effervescence  in  hot  hydrochloric  acid  as 
chloride  of  lead,  which  crystallizes  into  needles  on  cooling.  Dilute 
nitric  acid  easily  dissolves  white  lead  with  effervescence  and  an  escape 
of  carbonic-acid  gas.  White  lead  heated  on  a  knife  or  piece  of  metal 
turns  yellow.  Sulphuretted-hydrogen  fumes  in  the  air  turn  white  lead 
gray. 


82 


TESTS  FOR  WHITE  LEAD. 


Substance. 

Conduct  towards 

Heated  before  the 
Blowpipe. 

Muriatic  Acid. 

Caustic  Soda. 

Whiting  or  chalk 
in  any  form. 

Soluble      with 
effervescence. 

Unchanged. 

Becomes  incan- 
descent and  turns 
tumeric  brown 
after  cooling. 

Commercial  white 
leads.  Pearl  and 
other  whites.  Car- 
bonate of  lead,  etc., 
quick-process  leads. 

Soluble      with 
effervescence  and 
deposition     of 
small  crystals. 

Soluble     with- 
out residue,  or  if 
of   poor   quality, 
80   per  cent  will 
only  be  dissolved. 

Coating  formed 
on  the  charcoal 
is  citron-yellow 
while  hot,  sulphur- 
yellow  when  cold; 
is  easily  fused  with 
metallic  beads. 

Pattison's  white 
lead.  Lead  oxy- 
chloride. 

Same  as  above. 

Same  as  above. 

Same  as  above. 

Zinc  white  or 
oxide. 

Soluble,   no  ef- 
fervescence. 

Soluble     with- 
out residue. 

Yellow  while 
hot,  white  when 
cold. 

Antimony  white. 
Antimonious-  acid 
pigments. 

Same  as  above. 

Same  as  above. 

White,  easily 
volatilized,  me- 
tallic globules 
which  give  off 
white  smoke. 

Bone-ash,  Bone- 
black.  Phosphate  of 
calcium,  Ca.CPO^. 
(Basic  steel  furnace 
slag.) 

Soluble      after 
heating.       Effer- 
vescent at  first. 

Unchanged. 

Unchanged,  but 
becomes  incandes- 
cent. 

Barytes,  Blanc- 
Fixe,  mineral  white, 
and  other  pigments 
of  the  native  sul- 
phate of  barium. 

Unchanged. 

Unchanged. 

After  ignition, 
if  moistened  with 
muriatic  acid, 
gives  off  sulphur- 
etted hydrogen 
vapor. 

Gypsum  (Hy- 
drated  sulphate  of 
calcium). 

Unchanged. 

Unchanged. 

Incandescent, 
like  barytes.  If 
heated  in  a  tube, 
gives  water  vapors, 
etc. 

China,  pipe,  pot- 
ters', and  other 
clays. 

Unchanged. 

Unchanged. 

Incandescent, 
same  as  barytes 
and  gypsum.  If 
moistened  with  a 
solution  of  cobalt, 
and  heated  by  the 
blowpipe,  turns 
blue. 

SUBLIMED  LEAD.  83 

It  is  not  generally  known  that  dry  white  lead  and  oil  combine  with 
such  energy  that  if  linseed-oil  is  poured  upon  a  large  quantity  of  the 
lead,  and  the  mass  is  allowed  to  stand  a  few  hours,  the  temperature  of 
the  mass  becomes  so  high  that  the  oil  is  carbonized  and  colors  the  mass 
dark  or  even  black.  All  white-lead  paste  is  liable  to  turn  brown  if 
exposed  freely  to  the  air,  hence  should  be  kept  closely  covered,  or 
water  be  kept  on  the  paste  when  the  package  is  opened. 

Gmelin  states  "That  the  '  Old  Dutch  Process  '  white  lead  diffused 
through  water,  under  the  microscope  appears  as  non-crystalline, 
round,  and  oval  globules,  .0001  and  rarely  .0003  or  .0004  of  an  inch  in 
diameter,  while  in  the  quick-process  leads  the  globules  are  distinc- 
tively larger  and  more  transparent  and  crystalline." 

-  Dry  white  lead  is  tested  by  heating  100  grains  red  hot  and  stirring  it 
for  a  moment.  Its  loss  in  weight  by  driving  off  the  carbonic  acid  should 
be  from  13  to  16  grains.  If  more  or  less  loss  is  incurred,  the  lead  is 
probably  adulterated,  and  should  be  submitted  to  further  test  to  deter- 
mine the  character  of  the  adulterant,  as  shown  in  the  table  opposite. 

Sublimed  Lead,  PbSO^.    Specific  Gravity,  6.258. 

Sublimed  lead  is  a  by-product  obtained  in  the  smelting  of  non- 
argentiferous  lead  ores.  It  is  known  in  the  trade  as  Joplin  lead,  from 
its  place  of  manufacture,  Joplin,  Mo.;  also  as  Picher  lead,  from  the 
name  of  the  manufacturing  company.  It  is  made  in  two  colors — 
white,  suitable  for  all  purposes  that  the  hydrated  carbonate  of  lead 
is  used  for;  and  blue,  which  is  a  preferable  color  when  used  as  a  paint 
for  iron.  Both  colors  are  used  in  the  manufacture  of  india-rubber 
articles.  The  chemical  composition  of  sublimed  lead  is  sulphate  and 
anhydrous  oxide  of  lead,  both  amorphous;  the  good  qualities  of  the 
white  are  also  present  in  the  blue-colored  product.  There  is  a  small 
percentage  of  zinc  in  the  Missouri  lead  ores,  which  in  the  process  of 
smelting  is  converted  into  zinc  oxide  and  is  found  in  the  sublimed-lead 
product,  as  may  be  seen  in  the  analyses  of  a  sample  of  the  white 
product  given  on  page  84. 

The  blue  pigment  owes  its  color  to  the  lead  sulphide  and  car- 
bonaceous matter  from  the  bituminous  coal  used  as  a  fuel  in  the 
smelting-furnace. 

Sublimed  lead  is  prepared  in  special  furnaces,  the  process  being 
patented  and  known  as  the  "Lewis  and  Bartlett  Bag  Process  for 
collecting  lead  fumes."  The  process  has  been  mentioned  and  described 
in  more  or  less  detail  in  the  following  papers. 


84 


SUBLIMED  LEAD. 


Analyses  Substances. 


Averages. 


Substances,  Per  Cent. 


Sublimed  lead,  PbSO4.  .  . 
Protoxide  of  lead,  PbO . . 
"  zinc,  ZnO... 
"         "  iron,  Fe2O3.  . , 

Calcium  oxide,  CaO 

Carbonic  acid,  CO2 

Sulphuric  acid,  SO4. ...... 

Insoluble  matter 

Water 

Loss. . 


65.46  to  65.00  percent. 

25.85  25.89 

5.95  6.02 

0.03  0.03 

0.02  0.02 

1.53  2.00 

0.04  0.00 

0.08  0.08 

0.85  0.69 

0.19  0.27 


Metallic  lead,     71.831 
Metallic  zinc,  4.808 

20.508 


Carbonic  acid,  1.765 
Iron,  lime,  and  in- 

soluble matter,  0.130 
Sulphur,  water, 

and  loss,  0.958 


100.00 


Mineral  Resources  of  the  United  States,  1883-4,  p.  427;  Engineer- 
ing, 1884,  p.  495;  Engineering  and  Mining  Journal,  Vol.  XL,  1885, 
p.  4;  B.  und  H.  Zeitung,  Vol.  XLVII,  p.  346  (describes  the  works  of 
the  Bristol  Sublimed  Lead  Company,  Bristol,  England,  where  the 
process  is  in  operation) ;  Prerass  Zeitsch,  Vol.  XVIII,  p.  195;  Fresenius 
Zeitsch,  Vol.  VIII,  p.  148;  Transactions  of  the  American  Institute  of 
Mining  Engineers  (Washington  meeting,  February,  1890),  illustrated. 

The  galena  ore  is  first  smelted  with  coal  and  slaked  lime  in  the 
special  furnace,  using  an  air-blast  to  obtain  the  required  heat,  about 
800°  F. ;  the  hotter  the  fire  the  more  lead  is  volatilized,  and  the  more 
"fume"  is  produced. 

The  philosophy  of  the  process  is  that  galena  ore,  or  the  native  lead 
sulphide,  when  heated  to  nearly  a  white  heat,  vaporizes  slowly,  and 
the  vapors  in  contact  with  an  excess  of  air  passing  through  the  fur- 
nace burn  into  lead  sulphate.  Simply  heating  a  mass  of  galena  ore 
does  not,  however,  form  the  sublimed-lead  product.  When  the  ore 
is  properly  roasted  in  the  special  furnace  the  temperature  required 
to  effect  the  change  to  sublimed  lead  is  far  below  that  required  in  the 
vaporization  of  lead  sulphide.  The  ore  when  rapidly  heated,  even  if 
it  does  not  actually  vaporize,  has  a  tendency  to  do  so,  which  is  suf- 
ficient for  the  sublimation  process,  and  under  favorable  conditions  will 
burn  at  a  dull-red  heat. 

The  process  is  the  same  in  principle  as  that  used  in  the  collection 
of  the  oxide  of  zinc.  The  use  of  "fume"  from  the  smelting  of  lead 
for  a  pigment  is  very  old.  Bishop  Watkins,  in  his  scientific  works 
in  1778,  mentions  the  use  of  gray  fume  for  a  paint;  but  its  color  was 
then  objectionable  as  against  the  white  product  of  corroded  white 
lead  by  the  "Old  Dutch  Process." 

The  direct  fume-product  from  the  combustion  of  galena  ore  is  not 


SUBLIMED  LEAD.  85 

yet  sublimed  white  lead.  The  products  of  the  smelting-furnace  are 
pig  lead,  pasty  slags  containing  more  or  less  lead,  zinc,  and  other 
metallic  constituents  of  the  galena  ore  and  "fume."  The  latter  is 
drawn  off  by  an  exhaust-fan  through  a  settling-chamber  to  a 
bag-house  which  contains  a  large  number  of  woollen  bags  for 
filtering  the  fume  out  of  the  combustion  gases.  This  "fume"  is  a 
lead-colored,  impalpable  powder  known  as  "blue  powder.''  It  is 
ignited  and  allowed  to  burn  for  several  hours,  which  converts  it  into 
white  coherent  crusts.  These  crusts,  with  some  oxidized  ores,  set- 
tling in  the  flues  and  hearth  slags,  are  next  charged  into  a  special 
furnace  and  exposed  to  a  very  hot  coke  fire.  The  products  of  this 
smelting  are  pig  lead,  slags  poor  in  lead  as  waste  material,  and  the 
"fume,"  which  is  now  a  perfectly  white  impalpable  pigment  suspended 
in  the  air.  This  is  drawn  through  a  series  of  cooling  flues,  where  a 
further  purification  takes  place,  a  part  of  the  product  settling  and 
carrying  down  small  quantities  of  any  impurities  that  have  escaped 
the  action  of  the  heat.  The  sublimed  lead  is  now  arrested  by  forcing 
the  gases  and  lead  into  strainers  of  fine  textile  fabric,  where  the  gases 
escape  by  filtration.  The  sublimed  .lead  is  taken  from  the  strainers 
and  is  ready  for  the  market. 

The  process  assures  a  more  intimate  combination  of  the  vaporized 
atoms  of  the  lead  and  zinc  to  form  a  neutral  whole  in  which  every 
atom  is  approximately  of  the  same  physical  character  and  equally 
affected  by  any  of  the  causes  that  injure  a  paint,  than  is  possible 
in  a  pigment  formed  by  a  chain  of  partly  chemical  and  partly  mechani- 
cal operations  acting  upon  a  number  of  separate  substances  at  different 
stages  of  the  manufacturing  process.  Sublimed  lead  is  absolutely 
free  from  soluble  acids  or  sulphur,  is  amorphous,  non-crystalline,  and 
fine  and  smooth  in  the  character  of  its  atoms.  Being  a  pyrogenic- 
formed  substance,  it  is  not  affected  by  heat  or  deleterious  gases  of 
the  atmosphere  or  manufactories ;  does  not  turn  gray  on  long  expo- 
sure to  the  sunlight,  and  is  not  liable  to  chalk  like  corroded  white  lead. 
Though  it  dries  firm  and  of  almost  ivory  hardness  it  does  not  blister, 
crack,  and  peel  like  the  oxide  of  zinc  or  mixtures  of  zinc  oxide  and 
corroded  white  lead.  It  is  elastic,  mixes  thoroughly  with  the  oil,  and 
dries  well  without  an  excessive  use  of  driers,  either  metallic  or  liquid. 
Pound  for  pound  it  covers  better  than  white  lead,  and  keeps  its  color 
better,  as  the  following  comparison  of  painted  boards  exposed  to 
furnace  gases  shows.  The  action  of  the  weather  upon  sublimed  lead 
is  confined  to  the  surface  destruction  of  the  oil  vehicle.  Rain  and 


86 


SUBLIMED  LEAD. 


wind  do  not  affect  or  remove  the  pigment.  When  the  surface  of  the 
paint  shows  decay,  the  coating  can  be  repainted  without  removing 
the  old  paint.  Either  the  white  or  blue  products  of  sublimed  lead 
will  take  a  tint  more  uniformly  than  is  possible  with  any  mixtures 
of  white  lead  and  zinc  oxide  incorporated  by  the  usual  grinding  proc- 
esses. 


FIG.  15. — Sublimed  lead. 


FIG.  16. — Pure  corroded  white  lead. 


The  cuts  are  reproductions  from  a  photograph  of  a  picket  fence, 
each  alternate  picket  being  painted  with  the  different  leads  at  the 
same  time  arid  by  the  same  painter,  using  the  same  oil  as  a  thinner 
for  the  pastes,  and  the  same  driers,  a  separate  brush  being  used  with 
each  paint.  Three  coats  of  each  paint  were  applied,  each  being 
allowed  to  dry  thoroughly  hard  before  the  next  coating  was  spread. 
After  an  exposure  of  three  years  and  one  month  the  photographs 
were  taken.  The  cuts  are  magnified  ten  times.  The  chemical  reac- 
tion between  the  corroded  white  lead  and  the  oil  forming  a  lead  or 
paint  soap  is  clearly  apparent.  The  shrinkage  of  the  paint  soap 
has  caused  the  coating  to  crack.  Moisture  has  entered  and  loosened 
the  bond  of  the  paint  to  the  covered  surface,  while  the  soluble  char- 
acter of  the  lead  soap  has  caused  the  whole  coating  to  "  craze,"  and 
it  is  ready  to  fall  off  by  any  slight  mechanical  disturbance. 

The  sample  of  sublimed  lead  shows  that  no  reaction  (or  but 
little,  if  any)  has  taken  place  between  the  sublimed  lead  and  the 


SUBLIMED  LEAD. 


87 


FIG.  17.— Sublimed  lead. 


FIG,  18. — Pure  corroded  white  lead. 


88  SUBLIMED  LEAD. 

oil,  and  that  the  impervious  character  of  the  coating  has  kept  out 
the  moisture,  and  the  paint  is  still  firmly  bonded  to  the  wood;  the 
streaking  being  due  to  the  running  down  of  the  road  dust  when  wetted 
by  storms,  no  crazing  being  noticeable. 

Fig.  17,  sublimed  lead,  and  Fig.  18,  pure  corroded  white  lead,  are 
two-coat  applications  of  the  respective  paints  on  a  well-seasoned 
board  after  an  exposure  to  the  atmosphere  for  three  years. 


CHAPTER  VII. 

ZINC   OXIDE    (ZnO)    AND    OTHER   ZINC    PAINTS. 

Metallic  zinc  (Zn),  specific  gravity,  6.86  cast;  7.14  to  7.20  rolled  =  437.5 
pounds  per  cubic  foot;  combining  weight,  65.4;  tensile  strength,  5000  to  6000 
pounds  per  square  inch;  electrical  conductivity,  29.  It  melts  at  780°  F.  and 
begins  to  volatilize  in  the  open  air  at  800°  to  825°  F. 

ZINC  is  electro-positive  to  copper  and  iron,  whether  in  solution  or 
in  contact.  In  contact  with  iron  or  steel  it  forms  a  galvanic  pile  and 
decomposes  with  the  evolution  of  hydrogen.  It  is  used  in  this  form 
to  protect  steam-boilers  from  corrosion.  Each  pound  of  zinc  decom- 
posed evolves  5.6948  cubic  inches  of  hydrogen  that  weigh  210.29 
grains  and  develop  an  electrical  or  decomposing  energy  of  1.172 
horse-power  when  used  in  a  sulphuric-acid  battery  or  1.06  horse- 
power in  a  Bunsen  or  Grove  battery. 

This  electrical  energy,  while  not  so  strong  as  in  the  oxide  or  salts  of 
zinc  in  a  battery  form,  is  still  present,  and  is  recognized  by  painters 
as  "movement  in  the  paint,"  which  is  very  marked  with  zinc  pig- 
ments, as  will  be  hereafter  explained. 

Mallett's  experiments  determined  that  copper  and  zinc  plates  in 
contact  with  iron  increased  the  corrosion  of  the  iron  60  per  cent. 
Copper  alone  in  contact  with  iron,  40  per  cent.  Eisner  found  that 
the  oxides  of  tin,  zinc,  and  iron  used  together  in  a  paint  set  up  gal- 
vanic action  enough  to  crystallize  the  tin  into  flakes,  which  could  then 
be  rubbed  off. 

Zinc  is  associated  with  nearly  all  of  the  other  metals  as  a  mineral 
ore.  It  is  roasted  in  special  furnaces  and  by  processes  similar  to 
those  used  in  the  reduction  of  lead  ores  for  the  metal  or  its  oxides. 
The  presence  of  these  associated  metals  affects  the  quality  and  color 
of  the  oxides. 

The  native  carbonate  of  zinc  ore,  (Zn.C03)  (calamite,  zinc  spar), 
specific  gravity  4.45  to  5.0,  is  found  in  many  parts  of  the  world  in 
heavy  beds  as  crystals,  translucent  when  pure,  but  tinged  more  or 

89 


90  ZINC  OXIDE. 

less  gray,  green,  or  brown,  according  to  the  other  mineral  substances 
associated  with  it. 

Zinc  forms  but  one  oxide,  ZnO,  composed  of  zinc  80.344  per  cent 
and  oxygen  19.656  per  cent;  specific  gravity,  5.42. 

Zinc  oxide  is  produced  by  two  methods:  First,  by  the  oxidation 
of  the  metal  (French  process),  which  gives  a  more  dense  and  harder 
pigment  than  that  prepared  by  the  second  method — the  sublimation 
of  zinc  ore  (American  process).  The  product  from  the  first  process  is 
preferable  for  straight  oxide-of-zinc  paint;  the  second  is  better  for 
use  in  combination  with  other  pigments.  Both  varieties  grind  and 
mix  better  with  poppy-seed  oil  than  with  any  other  vehicle,  and  man- 
ganese-borate  drier  should  be  used  in  preference  to  lead  driers,  which 
are  liable  to  blacken  the  paint  on  exposure. 

In  both  processes  the  zinc  is  reduced  to  a  vapor  by  the  furnace 
heat  (about  850°  F.),  and  is  exposed  to  a  current  of  air  that  changes  it 
to  a  flake,  filament,  or  needle  form,  according  to  the  care  exercised  in 
the  process.  Some  of  the  particles  of  the  metallic  zinc  are  apt  to  be 
carried  over  in  the  vapor  unchanged,  mixed  with  the  atoms  of  carbon 
from  the  reduction  fire.  These  carbon-atoms  tend  to  give  a  gray 
color  to  the  product,  while  the  metallic-zinc  particles  are  subject  to 
an  attack  from  the  carbonic  acid  in  the  atmosphere,  forming  the  zinc 
carbonate  (ZnC03) ;  this  latter  change  occurring  in  the  pigment  after 
it  is  mixed  into  a  paste  or  paint. 

The  French  brand  of  zinc  oxide  (La  Vielle  Montague  Co.)  is  the 
best  in  the  world,  probably,  due  to  the  purity  of  the  metallic  zinc, 
the  care  exercised  in  its  reduction,  and  by  the  use  of  poppy-seed  oil, 
with  which  the  oxide  is  ground  immediately  after  its  formation. 

Most  of  the  American  zinc  ore  contains  lead,  tin,  antimony,  bis- 
muth, silver,  etc.,  the  oxidation  of  which  in  the  reduction  furnace 
produces  white  pigments,  but  they  are  all  blackened  by  sulphurous 
hydrogen,  which  affects  the  quality  of  the  zinc  product,  and  aids  in 
setting  up  the  electrolytic  action  that  all  zinc  substances  are  sensi- 
tive to,  as  before  stated.  Sulphur  is  also  present  in  many  zinc  ores, 
and  causes  a  yellow  color  in  the  oxide. 

History  of  Zinc  Oxide. 

In  1781  a  French  chemist  discovered  the  process  of  reducing  zinc 
to  an  oxide,  and  advised  its  use  instead  of  white  lead,  but  no  special 
results  followed. 


HISTORY  OF  ZINC  OXIDE.  91 

In  1796  an  Englishman  patented  a  zinc-combination  pigment,  but 
it  did  not  come  into  general  use  against  white  lead. 

In  1844  Leclair,  a  Frenchman,  made  zinc  oxide  and  founded  the 
La  Vielle  Montague  Zinc  Co.  Leclair  died  in  1872.  He  received  a 
gold  medal  from  the  Society  for  the  Encouragement  of  the  Arts,  and 
was  decorated  with  the  Grand  Cross  of  the  Legion  of  Honor  for  having 
improved  the  practice  of  painters. 

Leclair  disguised  the  fact  of  the  use  of  zinc  oxide  as  a  pigment. 
His  product  was  always  sold  as  white  lead,  a  precedent  that  mixed- 
paint  manufacturers  of  the  present  day  follow  but  too  well  if  the 
analyses  of  commercial  white  leads  given  in  Chapter  VI  are  any  indi- 
cation. 

The  Leclair  process  consists  of  volatilizing  the  metallic  zinc  in  a 
retort,  the  vapors  as  they  issue  from  it  being  met  and  mingled  with  a 
current  of  hot  air  from  a  blower  which  completely  oxidizes  them. 
The  resulting  products  of  combustion  are  led  through  a  series  of  flues 
and  chambers,  where  the  zinc  oxide  is  deposited  in  the  form  of  a 
flocculent,  impalpable  white  powder  ready  for  use  as  a  pigment. 

The  American  process  for  the  sublimation  of  zincite  ore  into 
zinc  oxide  was  invented  by  Mr.  Samuel  T.  Jones  in  1850,  who  con- 
structed a  furnace  for  effecting  this  purpose.  This  process  was 
improved  by  Col.  Samuel  Wetherell  for  the  purpose  of  working  the 
franklinite  ore  from  the  New  Jersey  deposits. 

Wetherell's  invention  embraced  a  special  furnace  and  a  process. 
The  zinc  ores  are  mixed  with  pulverized  anthracite  coal,  and  charged 
into  a  closed  furnace  having  a  perforated  grate,  through  which  an 
air-blast  furnishes  the  air  necessary  for  the  combustion  of  the  coal 
and  oxidation  of  the  zinc.  The  vapors  from  the  furnace  are  led 
through  a  number  of  flues  and  chambers,  where  the  coarser  particles 
are  deposited,  while  the  fine  air-floated  atoms  of  the  zinc  oxide  pass 
on  and  are  collected  in  a  number  of  fine  muslin  bags,  through  which 
the  combustion  gases  filter  away  to  the  atmosphere;  the  latter  part 
of  the  process  being  similar  to  the  Lewis  and  Bartlett  bag  process, 
used  in  the  production  of  sublimed  lead,  described  in  Chapter  VI. 
The  franklinite  and  zincite  ore  found  near  Mt.  Sterling,  N.  J.,  now 
furnish  most  of  the  American  zinc  oxide. 

About  44,000  tons  were  produced  in  the  United  States  in  1900, 
and  its  use  for  house-painting  is  increasing  at  the  rate  of  about  8  per 
cent  yearly.  The  New  Jersey  deposit  of  zincite  is  almost  absolutely 
free  from  lead,  antimony,  sulphur,  and  other  metals  that  affect  the 


92  QUALITIES  OF  ZINC  OXIDE. 

color  and  quality  of  zinc  oxide.  In  -France  its  use  has  almost  super- 
seded white  lead  for  interior  house-painting,  the  Government  pro- 
hibiting the  use  of  white  lead  for  this  purpose. 

Zinc  oxide  made  from  the  ore  is  used  more  extensively  than  that 
made  from  the  metal.  The  latter  not  only  dries  harder  and  is 
more  brittle,  but  on  large  surfaces  the  difference  in  the  whiteness 
of  the  coatings  is  very  apparent  and  in  favor  of  the  mineral  oxide. 
Zinc  oxide  mixed  with  water  tends  to  collect  in  lumps  or  masses. 
It  should  be  thoroughly  dry  before  being  ground  with  the  oil.  It 
does  not  unite  so  thoroughly  with  oil  as  lead  or  iron  pigments, 
nor  dry  as  quickly. 

One-third  of  one  per  cent  of  litharge,  added  to  the  linseed-oil 
in  which  zinc  oxide  is  ground,  renders  the  paint  more  elastic  and 
less  liable  to  peel. 

Mixtures  of  zinc  oxide,  white  lead,  and  ground  silex-barytes 
in  the  proportions  of  about  one-third  each,  prove  very  durable  in 
southern  climates  and  seacoast  exposures.  The  silex  gives  body 
to  the  paint,  but  being  transparent,  detracts  from  its  coloring  or 
covering  power.  There  is  less  white  lead  in  the  mixture  to  saponify 
with  the  linseed-oil  to  form  a  lead  soap  that  is  quickly  washed  away 
by  storms.  The  oil  also  dries  out  and  the  white  lead  is  rendered 
liable  to  chalk.  Such  coatings  cost  less  than  pure  white  lead,  are 
more  bulky,  and  by  a  little  extra  labor  on  the  painter's  part  can  be 
made  to  cover  more  surface  than  white  lead  and  zinc  oxide,  and 
they  save  oil. 

Zinc  oxide  50  per  cent,  white  lead  25  per  cent,  and  Blanc-Fixe 
25  per  cent,  also  stand  southern  and  seacoast  exposures  better  than 
white  lead  alone.  When  the  above  mixtures  are  used  on  wooden 
structures  the  barytes  and  silica  act  as  fillers  in  the  first  coat,  and  the 
percentage  of  either  substance  can  be  greater  than  in  the  other  coats. 

Pure  zinc  oxide  is  a  pure  white  pigment  but  little  affected  by 
sulphur  fumes,  and  does  not  yellow  the  oil  with  which  it  is  ground 
or  mixed.  It  is  of  itself  a  good  drier,  and  is  used  in  the  preparation 
of  kettle-boiled  oil.  When  it  forms  the  principal  pigment  in  a  paint, 
other  driers  are  detrimental,  as  the  coating  has  a  tendency  to  harden 
upon  the  surface  only,  and  remain  viscid  below  and  peel  readily. 
Linseed-oil  dries  harder  than  poppy-seed  or  walnut-oil.  In  zinc- 
oxide  and  white-lead  mixtures,  more  lead  than  oxide  will  be  required 
when  linseed-oil  is  the  vehicle,  in  order  to  keep  the  coating  elastic 
and  avoid  its  tendency  to  "  craze"  or  peel. 


QUALITIES  OF  ZINC  OXIDE.  93 

Zinc  oxide  carries  more  oil  than  white  lead,  hence  spreads  better 
and  reduces  the  tendency  of  the  lead  coating  to  chalk,  simply  be- 
cause there  is  less  lead  in  it  and  the  atoms  of  each  are  better  coated 
with  the  oil  from  the  larger  quantity  of  it  necessary  with  the  zinc 
pigment.  Mixed-zinc  oxide  and  white-lead  coatings  are,  in  general, 
more  durable  than  either  coating  alone,  provided  both  the  pigments 
are  pure.  As  zinc  oxide  costs  more  than  white  lead,  the  adulteration 
of  it  is  quite  as  general,  and  with  the  same  substances.  (See  Chap- 
ter VI.) 

It  deteriorates  by  long  keeping  and  loses  much  of  its  covering 
power,  which  can  be  restored  by  heating  the  pigment.  When  freshly 
made  or  heated  and  exposed  to  moist  air,  it  changes,  by  absorbing 
carbonic  acid,  into  the  carbonate  of  zinc  (ZnCO3).  Painters  say 
"it  spoils,"  and  guard  against  this  change  by  closely  covering  or 
sealing  it,  or  mixing  it  at  once  into  a  paste  or  paint,  where  the  oil 
protects  it,  except  those  particles  that  lie  upon  the  surface.  The 
carbonate  of  zinc  so  formed  is  crystalline,  loses  density,  and  hardens 
so  that  it  cannot  be  pulverized  or  ground  without  extreme  effort. 

In  this  change  81  parts  of  zinc  oxide  (ZnO),  composed  of  zinc 
80.344  per  cent,  oxygen  19.656  per  cent,  specific  gravity  5.42,  corre- 
sponding volume  14.9,  are  changed  to  equal  125  parts  of  the  carbon- 
ate of  zinc  (ZnCO3),  composed  of  zinc  52.153  per  cent,  oxygen 
38.278  per  cent,  carbon  9.569  per  cent,  specific  gravity  4.44,  volume 
28.1. 

This  chemical  change,  attended  by  so  large  an  increase  in 
volume  (nearly  double),  if  it  takes  place  after  the  oxide  has  been 
spread  as  a  paint,  the  whole  coating  will  be  loosened,  and  the  loose 
particles  will  be  carried  away  by  storms;  the  action  being  similar 
to  that  which  would  occur  should  the  sand  mixed  in  the  mortar  of 
a  plastered  wall,  when  dried,  change  its  volume  to  the  same  degree. 

Zinc  oxide  is  therefore  not  a  permanent  paint  for  open-air  ex- 
posures, but  for  interior  use  is  permanent;  for  though  carbonic  acid 
is  present,  the  moisture  is  absent,  both  elements  being  essential 
for  the  change  to  a  carbonate.  Dry,  gaseous  carbonic  acid  does  not 
affect  dry  zinc  oxide.  It  is  mixed  with  white  lead  for  interior  use 
to  lessen  the  tendency  of  the  white  lead  to  darken  by  absorbing  the 
sulphuretted  hydrogen  present  in  nearly  all  locations,  a  small 
amount  of  which  darkens  the  lead  pigment.  Such  coatings  are 
harder  than  the  lead  coatings,  as  the  surface  has  changed  in  the 
exposure  of  drying  to  a  carbonate  of  zinc. 


94  ZINC  SULPHIDE  AND  ZINC  SULPHATE. 

Zinc  oxide  is  a  hazardous  pigment  to  use  for  external  exposures 
when  mixed  with  iron  oxide,  lead,  or  other  color  pigments.  No 
process  of  mixing  them  can  so  associate  the  several  pigments,  even 
when  ground  in  the  oil,  as  to  enable  any  one  particle  of  either  substance 
to  thoroughly  protect  any  particle  of  the  others  present,  from  the 
changes  mentioned.  Atmospheric  moisture  and  gases  will  sooner 
or  later  reach  the  zinc  oxide,  whether  in  the  first  or  other  coats  of 
the  paint,  and  the  inexorable  laws  of  chemical  change  will  govern  the 
durability  of  the  coating,  the  ultimate  decomposition  of  which  will 
be  determined  simply  by  the  amount  of  zinc  oxide  present. 

Zinc  sulphate  (ZnSOJ  is  a  white  pigment,  and  is  often  produced 
in  the  manufacture  of  zinc  oxide,  the  color  of  which  is  not  affected 
by  its  presence,  even  if  the  sulphate  is  added  to  the  oxide  afterward. 
Zinc  sulphate  has  recently  been  brought  forward  as  a  desirable  pig- 
ment for  ferric  as  well  as  for  wooden  surfaces.  In  Germany  and 
England  it  is  used  largely  in  all  mixed  paints,  and  has  thus  far  proved 
to  be  very  resistant  to  atmospheric  influences  in  damp  locations. 
Like  zinc  oxide  and  the  lead  pigments,  its  cost  is  a  great  factor  against 
its  more  extended  use.  The  commercial  zinc-sulphate  paints  are 
adulterated  with  barytes,  the  natural  composition  of  which  is  favor- 
able for  its  admixture  with  the  sulphate. 

Zinc  sulphide  is  a  pigment  introduced  by  Mr.  J.  B.  Orr,  of  Eng- 
land. Its  composition  is,  barium  sulphate  70.50  per  cent  and  zinc  sul- 
phide 29.50  per  cent,  the  reactions  being,  BaS+ZnSO4  =  BaS04+ZnS. 
The  dense  white  precipitate  formed  is  highly  heated,  then  quenched 
in  water,  and  finely  ground  and  dried.  Becton  white,  Oleum  white, 
Orr's  white,  etc.,  are  zinc-sulphide  pigments.  Great  purity  of  the 
raw  materials  is  required  to  produce  a  purely  white  product. 

Zinc  sulphide  is  largely  used  in  the  manufacture  of  enamel  paints, 
linoleum,  table  oilcloths,  etc.  It  does  not  continue  to  oxidize 
after  mixing  with  linseed-oil,  as  do  lead  oxides,  and  can  be  considered 
as  a  saturated  or  non-siccative  compound.  It  does  not  combine 
with  resin,  and  therefore  will  not  saponify.  Exposure  affects  it  by 
blackening  the  paint  if  a  lead  drier  has  been  used  with  the  linseed- 
oil,  or  a  lead  pigment  associated  with  the  sulphide  pigment.  In 
these  cases  a  lead  sulphide  is  formed  which  is  dark-colored. 

Lithopone  or  Lithophone  is  a  German  paint  compound  only 
lately  manufactured  in  the  United  States.  As  a  commercial  mixed 
paint,  it  is  composed  of  sulphate  of  zinc,  zinc  oxide,  and  barytes  or 
Blanc-Fixe,  generally,  one-third  of  each  substance,  and  is  similar 


ZINC  SULPHATE  AND  LITHOPONE.  95 

in  character  to  Charlton's  white  and  Griffith's  patent  zinc  oxide- 
It  is  commercially  classed  as  Green  Seal,  Red  Seal,  Blue  Seal,  and 
Yellow  Seal.  The  Green  Seal  consists  of  one  part  zinc  sulphate 
and  two  parts  of  barytes.  The  Red  Seal,  of  one  part  zinc  sulphate 
and  three  parts  of  barytes.  The  specific  gravity  of  the  Red  Seal  is  4.2. 
The  Blue  and  Yellow  Seals  contain  some  zinc  oxide  with  the  sulphate, 
and  a  greater  percentage  of  barytes,  and  are  consequently  deficient 
in  covering  power.  The  large  amount  of  oil  taken  up  by  the  sul- 
phate and  zinc  oxide  is  counteracted  by  the  smaller  quantity  taken 
up  by  the  barytes. 

Barytes  costs  about  one-tenth  as  much  as  zinc  oxide  or  zinc  sul- 
phate, and  affords  every  requisite  to  grade  up  the  weight  of  zinc 
paints,  even  when  a  liberal  amount  of  whiting  is  present,  as  is  too  fre- 
quently the  case  with  most  mixed  pastes  or  color  paints.  (See  Tests  of 
Paints.) 

Green-seal  lithopone  approaches  closely  the  best  brands  of  French 
zinc  oxide,  and  does  not  require  so  large  an  amount  of  thinners  as  the 
American  brands  of  zinc  white,  and  it  works  easier.  It  is  unaffected 
by  sulphurous  gases,  and  does  not  turn  yellow  when  thinned.  It 
will  blacken  if  exposed  to  the  sun  before  it  is  dry.  Oils  or  driers 
containing  lead  or  copper  salts  turn  lithopone  gray;  neither  can  it 
be  used  with  other  colors  having  a  lead  or  copper  base. 

Griffith's  zinc  white,  a  chloride  or  sulphate  of  zinc,  is  precipitated 
from  a  soluble  sulphide  or  chloride  of  sodium,  barium,  or  calcium. 
No  iron  should  be  present.  The  precipitate  is  dried,  and  then  cal- 
cined at  a  low  or  cherry  heat,  with  careful  stirring;  raked  out  of  the 
furnace  and  quenched  in  vats  of  cold  water,  then  levigated  and  ground. 
It  is  an  oxysulphide  of  zinc ;  some  sulphate  of  magnesia  accompanies 
the  pigment. 

A  commercial  zinc  white  that  is  only  a  sulphate  of  zinc  is  made 
by  precipitating  the  pigment,  by  the  addition  of  a  dilute  solution  of 
sulphuric  acid,  to  an  acetic-  or  nitric-acid  solution  of  litharge.  Wash 
and  dry  the  precipitate  thoroughly.  The  clear  liquor  can  be  used 
repeatedly.  All  of  the  metals  associated  with  the  zinc  in  the  litharge 
are  dissolved  by  the  nitric  or  acetic  acids  and  precipitated  with  them 
as  sulphates,  and  are  inclined  to  blacken  on  atmospheric  exposure. 
The  zinc  pigments  formed  by  the  precipitation  processes  are  not  as 
durable  or  reliable  as  those  formed  by  the  oxidation  or  sublimation 
processes  from  metallic  zinc  or  the  zinc  ores. 

A  mixture  of  one  part  of  zinc  oxide  with  two  parts  of  red  lead 


96  ADULTERATIONS  OF  ZINC  OXIDE,  AND   TESTS. 

has  given  very  satisfactory  results  in  retarding  marine  corrosion  in 
both  salt  and  fresh  water.* 

The  United  States  Bureau  of  Construction  specifies  one  part  of 
white  lead  to  three  parts  of  zinc  oxide  for  the  paint  used  on  wooden 
structures  on  the  seacoast,  and  has  lately  abandoned  the  use  of 
zinc-oxide  pigments  on  ferric  structures  wherever  located.  House- 
painters  use  from  20  to  50  per  cent  of  zinc  oxide  when  they  mix 
their  own  colors.  The  great  percentage  of  zinc  oxide  in  the  com- 
mercial mixed-white  paints  and  colors  has  been  referred  to  in  Chap- 
ter VI. 

Adulterations  of  Zinc  Oxide,  and  Tests. 

Patent  zinc  white  is  a  sulphide  of  zinc  mixed  with  baryta  or 
strontia.  Fulton's  zinc  white  is  the  sulphide  of  zinc  and  barytes. 
Charlton's  zinc  white  is  the  same. 

In  the  adulterations  of  zinc  oxide  with  baryta,  barytic  white, 
permanent  white,  Blanc-Fixe,  constant  white,  etc.,  all  of  these  sub- 
stances are  artificial  sulphates  of  baryta,  and  are  less  crystalline  than 
the  natural  sulphate,  and  cover  better.  Pure ,  zinc  oxide  dissolves 
entirely  in  dilute  sulphuric  acid,  leaving  no  residue.  If  carbonate 
of  lime  is  present,  it  effervesces  with  muriatic  acid,  and  the  amount  of 
this  action  in  a  measure  indicates  the  amount  of  that  adulterant 
present. 

Zinc  oxide  lacks  weight  when  compared  with  white  lead  for  paint 
mixtures.  Barytes  in  its  powdered  form  supplies  this  deficiency, 
but  has  poor  covering  power;  it  spreads  well  and  saves  oil.  The 
floated  barytes — a  finer  grade  floated  from  the  pulverized  natural 
mineral — has  better  covering  power  than  the  ordinary  brands  of  this 
pigment,  simply  because  it  is  finer.  Artificial  barytes  or  "  Blanc- 
Fixe"  frequently  contains  pulverized  silica  or  white-glass  sand.  All 
of  these  substances  are  adulterants,  and  add  nothing  to  the  qualities 
of  zinc  oxide  except  weight  and  a  saving  of  oil  that  lessens  the  cost 
of  the  mixture  to  the  manufacturer,  but  seldom  to  the  consumer. 

To  test  a  mixed  zinc-oxide  paste  or  paint  for  adulterations,  repeated 
washings  with  benzine  or  ether  will  remove  the  oil;  then  dry  the 
residuum  on  blotting-paper.  Dilute  sulphuric  acid  completely  dis- 
solves zinc  oxide,  leaving  the  adulteration  or  any  other  metallic-base 
pigments  unaffected. 

*  "  United  States  Navy  Yard  Tests  of  Marine  Paints,"  Transactions 
American  Society  Mechanical  Engineers,  Vol.  XVI,  1894.  Paper  Number 
625,  p.  390. 


ADULTERATIONS  OF  ZINC  OXIDE,  AND  TESTS.  97 

A  dilute  solution  of  muriatic  acid  will  dissolve  the  lime,  if  any  is 
present.  The  barytes,  silica,  etc.,  will  remain  after  the  residuum 
has  been  ignited. 

On  a  painted  surface,  slightly  scratch  the  coating,  and  apply  a 
drop  of  sodium  sulphide  of  100°  Baume.  If  lead  pigments  are  present 
a  discoloration  will  follow  the  application  of  the  sodium. 


CHAPTER  VIII. 

LAMPBLACK. 

THE  carbon  group  of  pigments  comprises  lampblack,  mineral 
or  natural  asphaltum,  artificial  asphalt,  coal-tar,  and  graphite,  either 
alone  or  as  a  component  part  of  the  paint. 

Lampblack  is  the  fine  deposit  or  soot  formed  by  the  imperfect 
combustion  of  oil  or  fatty  substances.  Its  composition  varies  greatly, 
depending  upon  the  nature  of  the  substance  consumed  in  its  forma- 
tion, and  the  care  exercised  in  the  combustion  process.  Fatty  oils 
and  grease  yield  the  best  lampblack.  Coal-tar  yields  a  black  of  a 
brownish  hue  and  is  inclined  to  be  oily.  Resin  furnishes  a  good  black. 
If  the  combustion  is  forced  it  carries  along  some  of  the  free  resin- 
flakes,  and  yields  a  yellowish  resinous  black  of  an  inferior  quality, 
not  always  free  from  grit  and  dirt. 

Gas-black,  the  soot  product  from  the  combustion  of  hydrocarbon 
fuel  or  illuminating  coal-gas,  differs  in  molecular  structure  from  the 
fatty-oil  blacks.  The  gas-black  particles  appear  to  have  a  star  form, 
and  are  not  as  suitable  for  mixing  with  white  lead  or  zinc  white  for 
tints  as  the  fatty-oil  blacks,  though  their  color  is  densely  opaque. 
The  fatty-oil  lampblack  is  filament-formed,  and  incorporates  with 
the  oil  and  oxide  pigments  better  than  the  star  or  flake-formed  blacks. 
Gas-black  is  also  made  from  natural  gas  burned  under  revolving 
cylinders,  the  deposited  soot  being  removed  by  scraping.  With 
proper  care  the  lampblack  so  formed  is  nearly  pure  carbon.  In  a 
paint  coating  it  has  a  tendency  to  become  brittle,  crack,  and  flake 
off  after  a  short  time.  This  possibly  results  from  using  too  much 
drier  or  turpentine  in  the  vehicle,  as  of  itself  it  is  a  slow-drying 
pigment,  and  adds  no  drying  qualities  to  the  vehicle.  It  seldom 
appears  in  the  market  as  gas-black. 

Ground  soot  appears  as  a  lampblack  under  various  trade-names. 
It  contains  ammonia,  sulphuric  and  pyroligneous  acids,  rain- 
water, and  carbonic  acid.  Under  atmospheric  conditions,  solutions 
of  these  acids  are  produced  strong  enough  to  set  up  galvanic  action 

98 


LAMPBLACK.     (CARBON  GROUP  OF  PIGMENTS.)  99 

on  roofing  material  and  ferric  surfaces.  With  galvanized  iron  or 
sheet  zinc,  the  zinc  is  reduced  to  either  an  oxide,  sulphate,  or  carbon- 
ate at  the  expense  of  the  zinc  covering,  leaving  the  iron  exposed 
to  the  action  of  the  elements  which  produce  corrosion,  that  is  the 
more  active  because  of  the  galvanic  couple  of  the  different  metals. 
(See  Galvanizing,  Chapter  XVII.) 

Spanish  black,  or  cork-black,  is  made  from  the  combustion  gases 
of  burning  cork.  It  is  a  good  lampblack  in  color  and  texture  if  proper 
care  be  taken  in  the  process ;  but  charred  cork  and  ashes  are  too  often 
present  in  the  product  for  its  good. 

Ivory-black  is  made  from  chips  of  elephants'  tusks  and  other 
hard  bones  free  from  fat.  It  should  have  no  lustre,  as  that 
indicates  the  presence  of  unconsumed  fatty  matter.  Its  use  is 
almost  exclusively  for  the  preparation  of  the  finest  blacks  for  carriage, 
decorative,  and  artists'  colors.  Its  high  cost  debars  it  for  use  in 
ferric  coatings. 

Horn-black,  or  animal  black,  is  almost  identical  with  bone- 
black,  but  is  generally  in  a  more  finely  divided  state.  Ani- 
mal refuse,  albumen,  gelatine,  horn  and  hoof  shavings,  etc.,  are 
subjected  to  a  dry  distillation  in  a  still  or  retort;  the  black  carbo- 
naceous mass  left  is  washed  with  water  and  powdered  in  a  mill.  It 
requires  about  one  and  a  quarter  its  own  weight  of  oil  for  a  paste. 
The  great  quantity  of  oil  left  in  the  black  as  it  comes  from  the  still 
is  the  reason  for  its  slow  drying.  It  is  a  cold,  mild  black,  and  when 
not  well  burned  has  a  brown  tint,  dries  badly,  and  is  used  for  printers' 
ink,  blacking,  etc.,  also  for  the  cheaper  grade  of  black  varnishes  and 
paints.  ' 

Bone-black,  made  from  a  poorer  quality  of  bones  than  ivory-black, 
is  a  warm,  reddish-brown  black. 

Drop-black  is  an  ivory-  or  bone-black  blued  with  Prussian  blue. 

Charcoal-black  is  a  finely  powdered  beechwood  charcoal,  made 
in  Sweden,  and  generally  marketed  as  Swedish  black.  It  is  a  pure 
black  in  color,  but  has  less  covering  power  than  the  fatty-oil  blacks. 

Blue-black,  made  from  vine-stems,  is  a  better  quality  of  charcoal- 
black. 

Frankfort  black,  or  vine-black,  is  made  from  the  charcoal  left 
from  the  calcination  of  dried  vine  twigs,  wine  lees,  peach-stones, 
bone  and  horn  shavings,  etc.,  and  contains  potash.  It  varies  in 
shade  according  as  the  animal  or  vegetable  charcoal  is  in  excess. 
The  animal  matter  gives  it  a  brownish  hue,  the  vegetable  a  bluish 


100  LAMPBLACK.     (CARBON  GROUP  OF  PIGMENTS.) 

color;  both  have  a  good  covering  power.  The  finest  qualities  of 
this  black  come  from  the  condensed  gases  as  soot  in  the  calcination 
of  the  above  substances.  Many  other  process  blacks  are  sold  under 
the  above  names. 

Almond-black  is  made  from  fruit  stones,  nuts,  etc.  It  is  an  intense 
black,  and  has  the  same  qualities  as  Frankfort  black. 

German  black  is  made  from  the  combustion  gases  of  any  resinous 
matter,  which  escape  into  a  long  flue,  at  the  end  of  which  is  a  woollen 
or  other  fibre  hood,  that  collects  the  deposited  soot. 

English  black  is  collected  from  the  flues  of  bituminous  coke-ovens. 

Russian  black  is  made  from  the  soot  of  resinous  dead  fir-  or  pine- 
wood.  It  is  liable  to  spontaneous  combustion  if  left  for  a  short  time 
moistened  with  oil. 

Prussian  black,  Berlin  black,  ochre-black,  coffee-black,  earth-black, 
lake-black,  paper-black,  and  manganese-black  are  all  inferior  qualities 
of  lampblack  made  by  some  one  of  the  many  processes,  and  from 
the  many  substances  capable  of  slow  and  imperfect  or  smoldering 
combustion.  Their  color  and  qualities  are  quite  as  divergent  as 
their  names;  all  dry  slowly  with  uncertain  results  in  color  and 
lustre. 

Graphite-black,  or  ship's  black,  is  an  impure  lampblack  mixed 
with  an  inferior  quality  of  flake-graphite,  and  can  be  known  by  its 
metallic  lustre. 

Coal-  or  shale-blacks  are  generally  pulverized  slaty  bituminous 
coal. 

The  trade  adulterants  of  lampblack -consist  not  only  of  those 
substances  that  in  the  process  of  manufacture  are  imperfectly  car- 
bonized or  vaporized,  but  nearly  every  other  light  substance  that 
is  black  and  can  be  ground  to  the  required  fineness.  The  coarse  soot 
and  scales  deposited  in  the  chimneys  and  flues  from  the  combustion 
of  fatty- wood  and  soft-coal  fires,  coal-gas,  mineral  oil,  shale,  and 
asphaltum,  coal-tar,  etc.,  in  the  several  processes  of  distillation  or 
burning  for  other  products,  all  contain  ashes;  also  acetic,  pyroligneous, 
and  sulphuric  acids,  ammonia,  and  tar  to  a  notable  extent,  that  con- 
dense in  the  carbon-atoms,  and  materially  affect  the  color  and  quality 
of  the  lampblack.  These  are  not  always  removed  in  the  subsequent 
calcination  that  all  lampblacks  require  to  form  the  prime  pure 
product  known  as  "  burnt  lampblack."  These  acids  and  the  tar  pre- 
vent the  drying  of  any  lampblack  coating,  except  by  the  use  of  an 
excessive  amount  of  strong  driers.  In  such  cases  the  paint  hardens 


(  OF   THE      ' 

UNIVERSITY 


LAMPBLACK.     (CARBON  GROUP  OF  PIGMENTS.)  101 

only  on  the  surface,  and  remains  viscid  underneath,  and  is  prone  to 
peel. 

Anthracite  and  bituminous  coals  are  ground  and  marketed  as 
pure  lampblack.  They  contain  from  8  to  12  per  cent  of  ash,  also 
from  -J-  to  2  per  cent  of  sulphur,  and  absolutely  have  not  a  single 
quality  to  recommend  their  use  except  their  low  price.  From  the 
large  quantity  of  worthless  lampblack  selected  for  the  finishing 
coating  of  most  of  the  ironwork  in  the  New  York  Rapid  Transit 
Subway,  it  might  well  receive  a  special  trade-name  as  the  "Subway 
or  Tunnel  black." 

Carbon-black  appears  in  the  market  as  hydrocarbon-black,  Ameri- 
can gas-black,  satin-black,  gloss-black,  jet-black,  silicate  of  carbon,  etc. 

To  make  a  pure  lampblack  requires  not  only  a  proper  material, 
but  as  careful  attention  to  the  combustion  of  it  and  the  subsequent 
processes  for  its  preparation  as  the  manufacture  of  any  other  pig- 
ment. 

Pure  lampblack  made  from  a  fatty  oil  is  so  finely  subdivided 
naturally,  that  it  requires  no  grinding.  It  is  only  ground  in  the 
vehicle  to  secure  a  more  thorough  incorporation  than  is  possible 
by  stirring  it  in.  It  is  of  an  oily  feel  and  nature,  and  in  combination 
with  a  good  oil  forms  a  more  elastic  and  closer-clinging  coating  than 
any  other  pigment. 

It  is  chemically  and  electrically  passive,  non-hygroscopic,  non- 
corrosive,  and  less  affected  by  heat,  light,  and  peeling  than  any  other 
pigment. 

Its  life  ,hi  a  paint  coating  is  in  a  great  measure  exempt  from  all  at- 
mospheric influences  that  cause  the  decay  of  a  paint.  Its  elastic 
nature  reduces  the  frictional  element  due  to  the  beating  of  storms, 
while  the  oxidation  or  decomposition  of  organic  matter  in  the  dust 
and  from  other  sources  is  almost  nil.  It  remains  in  place  until  re- 
moved by  friction  or  the  destruction  of  the  vehicle,  and  can  be 
painted  over  without  the  expensive  torch-burning  or  scraping  so 
necessary  with  other  pigment  coatings. 

In  some  form  or  degree  of  purity  lampblack  enters  into  all  of 
the  black  varnishes,  enamels,  and  trade  paints  that  have  any  marked 
quality  for  the  protection  of  metallic  or  other  surfaces.  From  its 
finely  divided  state  and  oily  nature  it  is  liable  to  spontaneous  com- 
bustion, hence  must  be  stored  in  small  bulk  and  kept  well  covered. 
Lampblack  requires  more  than  double  its  own  weight  of  oil  to  secure 
a  good  coating;  it  is  easily  brushed  out  with  but  small  wear  of  the 


102  LAMPBLACK.     (CARBON  GROUP  OF  PIGMENTS.) 

brushes.  Driers  added  to  lampblack  paste  or  varnishes  should  be  in 
the  form  of  japans,  rather  than  turpentine,  which  flattens  the  lustre 
of  the  coating. 

Many  instances  are  on  record  where  a  single  coat  of  lampblack, 
like  that  used  for  the  lettering  and  symbols  on  the  old  cross-road  and 
tavern  sign-boards,  that  have  been  exposed  for  a  century  or  more, 
are  still  uninjured,  while  the  surrounding  colors  and  in  many  cases  the 
wooden  surface  of  the  sign  have  been  worn  away,  leaving  the  carbon 
lettering  in  full  relief. 

The  iron-link-chain  suspension  bridge  over  the  Merrimac  River 
at  Newburyport,  Mass.,  was  made  of  Norway  cold-blast  iron,  and 
erected  in  1810.  It  was  painted  with  two  coats  of  pure  lampblack 
and  raw  linseed-oil  over  sixty  years  ago,  and  is  still  (1903)  practically 
free  from  corrosion,  though  in  an  exposed  position,  subject  to  sea  air 
and  fog  influences  for  days  in  succession. 

The  use  of  lampblack  to  delay  the  "  setting "  of  red  lead  is  fully 
described  in  the  article  on  red  lead.  It  does  not,  however,  prevent 
the  failure  of  red-lead  coatings  when  they  are  exposed  to  the  action 
of  hydric-sulphide  fumes,  but  is  not  itself  affected  by  them. 

A  good  test  of  the  quality  of  a  lampblack  is  to  place  the  sample  on 
a  piece  of  blotting-paper  and  pour  a  little  ether  on  it  until  the  paper 
is  soaked  with  the  ether,  percolating  through  the  black.  If  on  the 
evaporation  of  the  volatile  and  removal  of  the  powder  the  under  side 
of  the  paper  appears  fatty,  the  lampblack  is  of  poor  quality. 

Animal  charcoal  and  bone-black  or  ivory-black  are  strong  bleaching 
agents,  and  it  is  possible  for  them  to  uncolor  overlying  coatings.  The 
oil  protects  them  somewhat  from  this  bleaching  influence,  but  where 
long  stability  of  color  or  lustre  is  required,  it  is  better  to  use  blacks  not 
of  an  animal  nature. 


CHAPTER  IX. 

MINERAL     OR     NATURAL     ASPHALTUM. — ARTIFICIAL     ASPHALT      (WHICH 
INCLUDES    COAL-TAR    AND    ITS    PRODUCTS,    PITCH,    MINERAL    WAXES, 

ETC.) . 

Mineral  or  natural  asphaltum.  There  are  a  large  number  of  these, 
known  as  Egyptian,  Bermudez,  Trinidad,  Mexican,  Cuban,  Cali- 
fornian,  Chinese,  etc.  They  all  vary  greatly  in  character  and  purity, 
and  are  the  residual  products  of  petroleum  when  the  light  hydro- 
carbon elements  have  been  evaporated  by  natural  causes.  They 
contain  vegetable  and  mineral  matter,  sulphuric  and  other  acids 
that  must  be  removed  by  boiling  or  distillation  to  render  them  suita- 
ble for  enamels,  varnishes,  or  paints.  Asphaltum  is  not  to  be  con- 
founded with  the  product  of  coal-tar  distillation,  called  "asphalt," 
which,  having  a  certain  resemblance  to  the  natural  asphaltum  in 
some  of  its  physical  qualities,  is  chemically  very  unlike  it.  The  name 
asphalt  being  carelessly  applied  to  both  the  natural  and  artificial  or 
coal-tar  product,  naturally  leads  to  some  confusion  on  the  subject. 
They  are,  in  fact,  so  widely  apart  in  all  their  essential  qualities  that 
they  cannot  be  appropriately  coupled  together  as  relating  to  the 
same  substance. 

The  characteristics  of  asphaltum  used  for  ferric  coatings  are 
briefly  given:  Asphalt,  bitumen,  or  mineral  pitch,  specific  gravity 
1  to  1.68,  softens  at  170°  F.  and  melts  at  212°  F.  (coal-tar  asphalt 
softens  at  115°  F.).  According  to  Boussingault  (Am.  Ch.  Phys.  [2], 
XIV,  141)  it  is  a  mixture  of  two  definite  substances,  viz.:  asphaltene, 
which  is  fixed  and  soluble  in  alcohol;  and  petrolene,  which  is  oily  and 
volatile.  The  greater  part  of  the  latter  may  be  volatilized  by  dis- 
tilling the  asphalt  with  water.  The  chemical  composition  of  bitumen 
is: 

Carbon 85  per  cent. 

Hydrogen.  ...    12     "     " 

Oxygen 3     "     " 


100     "     " 
It  is  therefore  an  oxygenated  hydrocarburet. 


103 


104  MINERAL   ASPHALTUM. 

It  is  the  petrolene  that  gives  the  cementitious  or  bonding  value  to 
compositions  into  which  it  enters.  Bermudez  asphalt  is  about  2  to  3 
per  cent  purer  than  Trinidad.  Samples  of  Bermudez  analyze  97.22 
per  cent  of  materials  soluble  in  bisulphide  of  carbon.  A  large  amount 
of  these  materials  is  also  soluble  in  ether,  showing  that  the  bitumen 
contains  large  amounts  of  petrolene. 

Petrolene  in  Bermudez  =  81. 63. 
"  Trinidad    =80.01. 

Egyptian  asphalt  is  the  purest  of  all  the  varieties  of  asphalt,  but 
is  not  procurable  at  present  in  commercial  quantities  required  for 
pavements  or  paints,  but  is  used  in  the  finer  qualities  of  japanned 
or  enamelled  wares,  baked  coatings,  varnishes,  etc.  Samples  of  it 
frequently  analyze  99.5  per  cent  of  soluble  matter. 

Asphaltum  yields  by  dry  distillation  a  yellow  oil,  consisting  of 
hydrocarbons  mixed  with  a  small  quantity  of  oxidized  matter.  It 
begins  to  boil  at  90°  C.,  but  gradually  rises  to  250°  C.,  giving  oils  of 
specific  gravity  during  the  boiling,  viz.  from  90°  C.  to  200°  C.,  specific 
gravity  =  0.817  (at  15°  C.) ;  that  which  boils  between  200°  C.  and  250° 
C.,  specific  gravity  =  0.868  (at  15°  C.);  both  portions  giving  by  analy- 
sis 87.5  carbon,  11.6  hydrogen,  and  0.9  oxygen,  which  is  nearly  the 
composition  of  the  oil  of  amber. 

These  asphaltum  oils,  treated  with  sulphuric  acid  and  then  washed 
with  potash  and  subjected  to  dry  distillation,  yield  a  number  of  oils 
which  are  insoluble  in  water,  or  strong  nitric  acid,  and  are  but  little 
affected  by  strong  sulphuric  acid,  but  are  very  soluble  in  alcohol  or 
ether. 

Asphaltum  has  no  metallic  base,  and  can  be  classed  as  a  gum  or 
resin,  hence  but  a  small  amount  of  it  can  be  incorporated  into  an  oil 
vehicle  for  use  as  a  paint.  Bisulphide  of  carbon  and  benzine  usually 
form  a  large  percentage  of  all  vehicles  in  asphaltum  paints. 

The  principal  merit  of  some  of  these  paints  consists  more  in  the 
name  than  the  quality.  If  it  is  once  considered  that  only  about  10 
per  cent  of  asphaltum  enters  into  the  composition  of  the  well-known 
street  pavements,  and  that  so  little  quantity  as  this  amount,  however 
it  may  govern  the  other  constituents  of  the  paving  compound,  has  to 
be  put  in  place  or  applied  hot,  and  cannot  be  used  or  compounded  in 
any  other  manner,  it  may  be  apparent  that,  notwithstanding  the 
catchpenny  name,  really  but  little  if  any  asphaltum  of  either  high  or 
low  degree  ever  enters  into  the  composition  of  any  of  these  paints. 


MINERAL  ASPHALTUM. 


105 


Analyses  of  many  of  these  paints  show  that  there  is  not  5  per  cent 
of  asphaltum  in  the  composition  of  any  brand  of  such  paint  upon  the 
market.  Even  with  this  small  amount,  and  with  the  best  of  boiled 
or  raw  linseed-oil  as  the  vehicle,  the  paint  is  difficult  to  dry  without 
the  use  of  strong  metallic  salts  mixed  with  the  oil  to  aid  its  oxidizing 
or  drying  quality;  and  if  a  quick-drying  paint  is  wanted,  these  oxidiz- 
ing materials  are  added  in  such  amounts  as  to  materially  affect  the 
life  of  the  paint. 

When  the  color  of  the  paint  is  other  than  black  or  steely  gray,  it 
may  be  doubted  if  any  asphalt  will  be  found  present  under  the  closest 
analysis;  and  the  red  and  brown  colored  samples  will  be  found  to 
rely  almost  wholly  upon  oxide  of  iron  as  the  base  of  the  pigment, 
under  whatever  name  it  may  be  masked. 

Gilsonite,  a  mineral  resin  associated  with  natural  asphaltum,  is 
used  largely  as  the  principal  pigment  in  these  paints.  Gilsonite, 
asphaltum,  petroleum,  cannel  and  bituminous  coal  and  shale,  all  shade 
off  into  each  other  so  gradually,  and  form  so  numerous  a  class  of  bitu- 
minous mineral  substances,  that  it  is  difficult  to  determine  their  exact 
relations.  The  fluid  elements  of  the  hydrocarbons  evaporate,  and  as 
the  heavier  portions  solidify,  they  oxidize  with  a  loss  of  hydrogen, 
and  change  until  over  a  hundred  different  bituminous  mineral  sub- 
stances can  be  determined  from  the  hydrocarbon  group. 

The  general  composition  of  the  numerous  class  of  petroleums, 
after  the  evaporation  of  the  lightest  hydrocarbons  by  nature  in  the 
form  of  natural  gas,  is,  viz.: 


Crude  Oil  26°  Baume.    Distillates. 
Commercial  Names. 

Approx- 
imate 
Degree. 
Baume. 

Specific 
Gravity. 

Weight  of  1 
U.  S.  Gall,  in 
Pounds. 

Percent- 
age Ob- 
tained. 
Approx- 
imate. 

Gasoline                                        

75-76 

0.6820 

5.69 

3-5 

Benzine                                                 .  •  • 

63 

0  .  7253 

6.04 

4-6 

Kerosene  (illuminating-oil)                  .  . 

45 

0.80 

6.66 

13-15 

Heavy  kerosene  (mineral  sperm)  
Gas  distillate     .                  

38-40 
28 

0.8333 

0.8866 

6.94 

7.38 

8-56 
10-18 

Light  lubricating  (spindle-oil)  
Neutral  oil                       

26 
23 

0.8974 
0.915 

7.48 
7.62 

8-10 
10-12 

Heavy  lubricating-oil  

21 

0.9271 

7.72 

5-6 

Valve  lubricating-oil.  

14-15 

0.9655 

8.04 

4-5 

Asphalt  (crude)  ,  containing  4  to  7  per  ) 
cent  of  sulphur                                  f 

11-6 

1  to  1.60 

8.344  to 
13  350 

11-12 

Loss  .                                                   ' 

5  to  13 

Other  samples  of  petroleum  range  from  5°  to  6°  Baume  higher, 
and  carry  more  hydrocarbons  of  the  paraffin  series. 


106  ARTIFICIAL  ASPHALT   AND   COAL-TAR. 

The  illuminating  parts  of  these  oils  carry  more  carbon,  and  less 
hydrogen,  and  give  a  smoky  flame,  due  to  the  fact  that  it  requires 
more  oxygen  to  effect  complete  combustion  of  the  carbon  element 
than  it  does  to  consume  the  hydrogen. 

Coal-tar  is  a  generic  term  applied  to  those  bitumens  which  are 
extracted  during  the  destructive  distillation  of  bituminous  coal  for 
gas  or  coke.  Commercially,  the  name  is  also  applied  to  water-gas 
tar.  The  nature  of  the  tar  varies  with  the  nature  of  the  coal,  and 
with  the  processes  employed  in  its  production  as  a  waste  product  in 
the  manufacture  of  gas  or  hard  coke. 

There  is  no  known  method  of  describing  accurately  the  true  com- 
position of  the  coal-tars.  No  two  are  identical  in  every  respect, 
although  many  are  identical  in  every  essential  respect.  Variations 
also  occur  from  the  admixture  with  the  coal  in  process  of  distillation, 
of  greater  or  less  quantities  of  oils  of  various  kinds,  used  for  the  pur- 
pose of  enriching  the  gas.  The  tars  vary  in  the  amount  of  bitumen 
they  contain  within  the  limits  of  60  to  92  per  cent;  also  vary  largely 
in  the  percentages  of  oil  which  they  contain,  and  in  the  quality  of  the 
oil.  The  non-bituminous  matter  in  the  tar  is  generally  carbon, 
which  is  synonymous  with  lampblack,  and  was,  of  course,  a  hydro- 
carbon before  the  hydrogen  was  eliminated  by  combustion.  Coal- 
tar  cement,  or  asphalt,  is  a  residue  from  the  distillation  of  coal-tar. 
Its  hardness  or  flexibility  is  due  to  the  percentage  of  the  oil  left  in  it, 
and  may  vary  from  16  per  cent  in  one  quality  of  coal-tar  to  52  per 
cent  in  another.  One  per  cent  of  oil  taken  from  one  coal-tar  will 
produce  a  greater  hardening  effect  than  l£  per  cent  taken  from 
another  tar,  and  the  degree  of  heat  necessary  for  distilling  off  the 
oil  may  vary  from  200°  to  600°  F.,  even  when  supplemented  by 
mechanical  agitation,  or  by  blowing  superheated  steam  or  air  into 
the  still  during  the  distillation  process. 

The  average  analyses  of  a  large  number  of  samples  of  coal-tar 
from  coal-gas  retorts  gave  for  a  40-gallon  barrel,  specific  gravity  1.08— 
1.10: 

1£  gals.,  or  3.75%,  of  light  oils,  consisting  of  benzole,  naphtha,  and  carbolic  acid. 
9£  gals.,  or  23.75%,  of  heavy  oil,  consisting  of  creosote-oil  and  anthracine,  etc. 
29  gals.,  or  72.5%,  pitch. 

Boiled  in  open  kettles,  this  tar  should  be  reduced  from  15  per 
cent  to  25  per  cent,  according  to  the  duty  required  of  it.  The  tar 
resulting  from  the  distillation  of  petroleum  oils  for  water-gas  is  of 
a  decidedly  inferior  quality  to  that  obtained  from  gas-coals,  and  is 


ARTIFICIAL  ASPHALT  AND  COAL-TAR.  107 

better  adapted  for  coating  the  cruder  forms  of  wood  constructions, 
piles,  dock-timbers,  fence-posts  in  the  ground  part,  than  metal-work. 
But  this  same  oil-tar,  if  distilled  at  heats  from  600°  to  800°  F., 
forms  a  pitch  of  almost  adamantine  hardness  when  cold,  and  resists 
almost  all  corrosive  agents  and  solvents  except  those  of  the  hydro- 
carbon class. 

Analysis  of  a  by-product  coke-oven  tar: 

Naphthalene 12. 00  per  cent 

Anthracine 0. 30  "  " 

Tar  acids 7. 00  *'  " 

Tar  bases 1 . 60  "  " 

Water 2.00  "  " 

Pitch 77.10  "  " 

100.00    "      " 

When  the  concentration  of  the  gas  coal-tar  is  carried  to  the  25 
per  cent  or  30  per  cent  stage,  the  product  is  comparatively  odorless, 
or  at  least  is  not  any  more  objectionable  than  that  from  oil  paint, 
the  pungency  due  to  the  light  oils  and  carbolic  acid  being  dissipated. 
In  the  distillation  of  coal-tar,  until  the  final  residuum  of  coke 
is  reached  in  the  still,  there  are  no  constituent  oils  derived  from 
the  process  that  do  not  gradually  volatilize  by  the  heat  of  the  sun 
or  approximating  temperatures;  and  all  coal-tar  or  hydrocarbon 
products  suitable  for  use  in,  or  as  paints,  also  become  fluid  when 
exposed  to  heat;  in  fact,  but  few  of  them  are  applied  in  any  other 
condition  than  while  hot.  They  are  all  liable  to  run  on  vertical 
or  slightly  inclined  surfaces,  until  by  evaporation  they  are  so  ad- 
vanced on  the  road  to  brittleness  that  they  solidify,  and  by  a  little 
further  progress  in  the  same  direction  they  become  brittle  and  scale 
off  on  the  least  mechanical  disturbance. 

In  the  production  of  an  ordinary  standard  roofing-pitch  from  a 
coke-oven  tar,  the  distillation  ran,  viz.: 

Water 1 . 49  per  cent 

Light  oil  (to  325°  F.) 3.04    "      " 

Heavy  oil  (above  325°  F.) 21.47    "       " 

Pitch  (at  585°  F.) 74.00    "      " 

100.00    "      " 


108  ARTIFICIAL  ASPHALT   AND   COAL-TAR. 

The  pitch  contained  about  12  per  cent  of  free  carbon.  Coal-tar 
asphalt  softens  at  115°  F.  Natural  or  mineral  asphalt  softens  at 
150°  to  170°  F. 

Analysis  of  a  standard  coal-gas  tar  (specific  gravity  1.24): 

Carbon. 89 . 21  per  cent 

Hydrogen 4. 95    "      " 

Nitrogen 1.05    "       " 

Oxygen 4.23    "       " 

Ash trace 

Volatile  sulphur 0. 56    "       " 

100.00    "       " 

In  combustion  it  gave  British  thermal  units  15.781.  Evaporative 
power  from  and  at  212°  F.  =  16.4  pounds  of  water. 

Analysis  of  water-gas  tar  from  gas-oil  (specific  gravity  1.15): 

Carbon 92.  70  per  cent 

Hydrogen 6. 13    "       " 

Nitrogen 0.11    "       " 

Oxygen 0. 69    "      " 


Ash trace 

Volatile  sulphur 0. 37    "       " 


100.00    "       " 

In  combustion  it  gave  British  thermal  units  17.193.     Evaporative 
power  from  and  at  212°  F.  =  17.8  pounds  of  water. 

In  the  distillation  of  an  oil  water-gas  tar  by  Dr.  John  F.  Wing, 
the  products  obtained  at  the  several  stages  of  the  process  were  as 
follows  (specific  gravity  of  the  crude  tar  13.5°  Baume—  1.1 — water  1) : 
Distillation  heat,  F.  Percentage  of  distillate. 

240°  F.  water 0. 25  per  cent 

240°  F.  light  oil 4.25    "       " 

240°  to  336° 0. 50    "       " 

336°  "  400° 3.00    "       " 

400°  to  550° 29. 00    "       " 

550°  il  617° 5.00    "       " 

617°  "  690° 17.00    "       " 

Above  700°  a  hard-pitch  residue 41 . 00    "       tl 

100.00    "      " 


ARTIFICIAL  ASPHALT  AND  COAL-TAR.  109 

At  400°  F.  the  distillate  became  heavier  than  water.  The  residues 
obtained  at  temperatures  of  550°  to  617°  F.  were  soft  pitch,  but  would 
not  flow.  There  were  from  12  to  15  per  cent  of  free  carbon  in  the  oil- 
gas  tar,  while  5  to  8  per  cent  are  the  usual  amounts  found  in  an  Otto- 
Hoffman  coke-oven  coal-tar. 

The  acids  and  ammonia  salts  in  crude  coal-tar  must  be  eliminated 
by  boiling  or  distillation  when  used  for  coating  ferric  bodies.  If 
they  are  not  removed,  the  tar,  either  hot  or  cold,  is  one  of  the  most 
unreliable  and  unmanageable  of  coatings.  (See  Dr.  Angus  Smith's 
experience,  Chapter  XII.) 

The  mineral  waxes  derived  from  coal-tar  are  the  most  reliable 
of  all  the  coal-tar  paint  products.  They  are  especially  not  affected 
by  "sweating."  They  are  an  intermediary  substance  between  the 
fluid  and  volatile  elements  and  the  heavy  ones;  and  retain  some  of 
the  volatile  element  that,  as  it  slowly  evaporates,  causes  the  paraffin 
to  crack  badly  and  change  its  volume.  The  spaces  between  the 
tension-chord  and  other  eye-bars  in  modern  bridge  constructions,  lying 
so  closely  together  as  to  be  incapable  of  inspection  or  repainting  to 
protect  them  from  corrosion,  are  often  filled  in  with  melted  paraffin 
as  a  protection  from  rust.  It  requires  but  a  short  period  for  the  wax 
to  harden,  shrink,  and  crack,  and  expose  the  ferric  bars.  As  well 
expect  a  cracked  varnish  coating  to  protect  the  surface  it  covers, 
as  one  of  cracked  paraffin. 


CHAPTER  X. 

ASPHALTUM  PAINTS  AND   CARBON  VARNISHES. 

ASPHALTUM  paints  are  proprietary  products,  and  vary  in  composi- 
tion and  quality  quite  as  much  as  does  the  substance  from  which  they 
derive  their  name.  There  is  no  standard  of  excellence  in  asphaltum 
paints. 

A  small  amount  of  some  quality  of  mineral  asphaltum  or  gilsonite, 
mixed  with  varying  amounts  and  qualities  of  the  trade  lampblacks, 
constitutes  the  pigment  for  the  numerous  brands  of  quick-drying 
paints  used  to  blacken  a  large  class  of  ferric  bodies  that  need  a 
coating  for  appearance  rather  than  protection  from  corrosion.  The 
catchy  name  often  secures  their  use  on  more  important  structures, 
where  the  price  at  which  they  are  offered  should  promptly  condemn 
them  before  trial. 

A  supposed  better  class  of  asphaltum  paints  or  so-called  var- 
nishes, similar  to  the  "Maltha,"  "  P.  &  B.,"  and  other  trade-mark 
designations,  are  freely  marketed  as  superior  paint  products.  They 
are  in  no  sense  varnishes,  but  simply  the  above-mentioned  class  of 
pigment  substances,  mixed  with  bisulphide  of  carbon,  benzine,  and 
other  uncertain  hydrocarbon  liquids  and  oils,  the  latter  often  con- 
taining more  resin-oil  than  linseed-oil.  They  are  not  compounded 
by  heat,  as  all  true  varnishes  are.  They  have  had  an  extended  trial 
for  over  fifty  years  on  important  ferric  structures, — naval,  hydraulic, 
and  other  work,  only  to  fail  after  a  brief  exposure.  Wherever  placed 
in  competition  with  other  carbon  or  metallic-base  coatings  they  are 
invariably  found  low  in  the  column  of  merit.  As  a  rule  they  spread 
easily  and  show  well  at  first,  but  when  the  volatiles  have  evaporated, 
especially  if  they  have  been  subjected  to  a  moderate  heat  test  140°  to 
180°  F.,  they  become  brittle,  turn  brown,  crumble,  and  are  easily 
removed.  The  application  of  these  paints,  containing  bisulphide 
of  carbon,  is  attended  with  extreme  danger  from  fire,  even  on  external 
exposures.  The  vapor  of  bisulphide  is  very  explosive  at  low  tem- 
peratures, also  disastrously  injurious  to  the  painters  or  others  breath- 
ing it  during  the  application  of  the  paint  in  any  confined  space,  and 

only  moderately  less  so  in  the  open  air. 

110 


FIG.  20. — Animi  Fossil  Resin. 


FOSSIL  RESINS.  Ill 

An  account  of  its  application  to  water-mains,  where  it  resulted  in 
the  insanity  and  death  of  a  number  of  the  painters  and  workmen 
engaged  in  painting  and  laying  the  pipes;  also  in  the  utter  failure  of 
the  coating  to  protect  the  same  pipes  from  corrosion,  is  given  in  "Trans- 
actions American  Society  Mechanical  Engineers,"  Vol.  XVI,  1895, 
Paper  637.  Also  in  Engineering  News,  Feb.  7,  1895,  and  April  4, 1895. 

A  further  demonstration  of  the  inferiority  of  these  asphaltum 
paints  in  competition  with  other  oil  paints  and  black  varnishes  is 
given  in  a  series  of  tests  made  by  Mr.  Max  Toltz,  C.E.  The  Report 
was  read  before  the  Society  of  Civil  Engineers,  St.  Paul,  Minn.,  and 
reported  in  the  Journal  of  the  Association  of  Engineering  Societies, 
1897.  It  was  also  briefly  referred  to  in  "  Transactions  American 
Society  Mechanical  Engineers/'  May,  1901.  (See  also  Bisulphide  of 
Carbon,  Chapter  XX.) 

Asphaltum  varnishes  or  carbon  paints  in  which  the  vehicle  is 
practically  a  linseed-oil  varnish,  compounded  by  heat,  and  of  the  same 
nature  as  a  baked-japan  vehicle  in  which  the  carbon-blacks  and 
other  pigments  are  ground,  are  very  reliable  for  protective  coatings. 
They  seldom  fail  under  the  severest  tests  of  marine  or  other  corrosive 
exposures. 

Fossil  Resins. 


•&~- 

FlG'  I?-—  Section  through  a  resin  passage  of  Abies  excelsa  (fir-  and  spruce-trees). 
The  cavity  Hg,  as  well  as  the  thin-walled  cells  Hp,  are  filled  with  semi- 
fluid resm.  The  thick-ll 


,  -  , 

fluid  resm.     The  thick-walled  cells  P  contain  starch. 

Fossil  gums  or  resins,  under  the  general  name  of  Copals,  are  those 
used  for  varnishes  or  varnish  paints.  They  are  incorporated  by 
heat  with  refined  linseed-oil,  and  when  black  generally  contain  a 
quantity  of  the  better  class  of  refined  asphaltum. 

The  oldest  and  hardest  of  the  fossil  resins  is  Zanzibar;  the  trees 
that  furnished  it  are  extinct. 


112  FOSSIL  RESINS. 

There  are  about  thirty  different  resins  used  in  paint  and  varnish 
manufacture,  many  of  them  possessing  peculiar  qualities.  The  best 
are  the  fossil  resins  found  in  the  beds  of  rivers  or  in  the  earth  where 
they  have  lain  for  centuries.  The  hardness  of  these  fossil  gums  appears 
to  depend  upon  their  age  and  the  pressure  that  they  have  undergone 
while  buried.  Amber  is  the  hardest  and  most  valuable  of  all  resins. 
Only  the  refuse  of  black  amber  is  used  for  varnish.  Amber  varnish 
merely  means  amber-colored  varnish.  There  is  no  amber  in  the  com- 
mercial brands. 

Copal  is  the  next  in  hardness;  it  comes  from  Zanzibar,  and  is 
known  in  the  English  trade  as  "Animi,"  from  the  insects  embedded 
in  it.  Being  very  difficult  to  dissolve,  it  is  distilled  until  it  loses 
from  20  to  25  per  cent,  when  it  can  be  dissolved  in  boiling  oil.  There 
are  three  varieties  of  it,  and  many  grades. 

"Animi"  is  now  the  technical  name  for  the  South- American 
copal,  and  comes  from  Brazil. 

Sierra  Leone  copal  has  nothing  to  do  with  Sierra  Leone  except  for 
its  name.  It  comes  from  the  river-beds  in  the  interior  of  Africa. 
It  is  the  only  African  resin  that  will  dissolve  in  cold  alcohol.  Its 
color  is  not  as  good  as  the  Zanzibar  or  best  Kauri,  but  it  is  harder 
than  the  Kauri.  It  is  mixed  with  the  Zanzibar  for  hardness,  itself 
giving  toughness  to  other  fossil  resins. 

Other  African  copals  are  the  Pebble  or  Pebble-stone — which  is  the 
hardest — Acora,  Loango,  Gaboon,  Congo,  Benguela,  and  three  sorts 
of  Angola. 

Manila  is  of  two  kinds, — a  hard  and  a  soft;  neither  are  fossil 
gums.  They  come  from  the  Philippine  and  other  islands,  Borneo, 
Singapore,  etc.  This  gum  can  be  used  as  it  comes  from  the  living 
tree  like  the  crude  resin  from  the  American  long-leaf  pine. 

Dammar  is  a  recent  resin  from  trees  not  extinct,  and  contains 
the  most  water.  When  it  forms  the  principal  resin  in  a  varnish  or 
varnish  paint,  it  appears  to  be  always  drying,  hence  the  danger  to 
any  other  coating  spread  over  it.  It  is  the  resin  used  with  enamel 
paints  to  give  the  high  gloss  characteristic  of  these  coatings. 

Sandarach  is  a  resin  yielded  by  the  barberry-trees  of  Northern 
Africa.  It  is  used  to  a  considerable  extent  as  the  basis  of  spirit  var- 
nishes. 

Kauri  or  Cowrie,  from  New  Zealand,  is  the  principal  fossil  resin 
used  for  a  varnish,  being  about  ten  times  the  amount  of  all  the  other 
resins  combined.  It  is  produced  from  a  species  of  tree  riot  yet  extinct, 


FOSSIL  RESINS.  113 

but  the  gum  as  it  exudes  from  the  tree  at  the  present  day  is  of  no 
more  value  for  a  varnish  than  that  from  the  common  spruce-tree ;  but 
when  it  has  lain  in  the  earth  for  centuries  it  becomes  hard  and  valu- 
able. It  is  very  indifferent  to  the  action  of  sulphur  gases,  and  is 
more  colorless  than  the  other  fossil  resins.  It  is  easily  dissolved, 
and  melts  more  readily  than  mastic,  but  less  so  than  the  common 
resins.  It  is  allied  in  composition  to  Dammar  resin,  and  is  from 
two  to  nine  times  cheaper  than  the  other  fossil  resins  whose  prices 
range  in  the  order  of  commercial  quantities  as  follows : 

Prices  per  pound. 

First.      Kauri 10  to  50  cents. 

Second.  Manila 10  "  25      " 

Third.     Dammar 16  "  25      " 

Fourth.  Zanzibar,  best $1  "  $1 . 25 

Fifth.     Benguela 85  "  90  cents. 

The  general  composition  of  all  fossil  or  other  resins  is  C20H40O2. 
Their  specific  gravities  at  60°  F.  are: 

Yellow-leaf  pine-resin  (dark  colophony).  .  .  .  1.100 

"          "       "        "    (whitish  opaque) 1.047  to  1.044 

"          "       "        "    (yellow  transparent).  .  1.084  "  1.083 

Shellac,  D.  C.  (dark  colored) 1 . 123 

"        L.  C.  (light  colored) 1. 114  "  1. 113 

"        B.       (bleached) 0. 968  "  0. 965 

Copal,  East  Indian 1.070  "  1.063 

"     West  Indian 1.080  "  1.070 

"      Very  old 1,055  "  1.054 

"     Zanzibar 1 .068  "  1.067 

Dammar,  Manila 1.121  "  1.062 

"        old 1.075 

Benzoin,  Siam 1.235 

Pehang 1.155  "  1.145 

Borneo 1. 170  "  1. 165 

Guaiacum,  pure 1.237  "  1.236 

Tolu,  old  and  brittle 1.232  "  1.231 

Amber 1.094  "  1.074 

Sandarach 1.044  "  1.038 

Mastic 1 .060  "  1.056 

Angola 1.081  "  1.064 

Kauri  (Australian) 1. 115  "  1.050 

Brazilian 1.082  "  1.018 

Shellac  is  an  animal  resin  produced  from  the  banyan-  or  fig-tree 
and  other  trees  of  India,  called  "  Lac-trees."  Lac  is  the  root  of  the 
word  Lacquer,  of  Indian  derivation,  and  was  probably  first  applied 


114 


FOSSIL  RESINS  AND  SHELLAC. 


to  specimens  of  Chinese  lacquer-ware,  imported  through  India.  The 
branches  of  the  lac-trees,  when  stung  by  the  female  insect  Coccus- 
lacca,  exudes  a  sap  that  the  insect  transforms  by  digestion  into  a 
resinous  excretion  (lac),  with  which  she  encrusts  her  eggs  and  herself. 
The  insect  is  indigenous  to  the  forests  of  India.  The  exudation  of 
the  sap  from  the  lac-tree  is  somewhat  similar  to  that  produced  by 
an  insect  or  parasitic  fungus  on  a  species  of  oak  (the  gall-oak)  that 
produces  the  " gall-nut"  used  by  dyers  and  in  pharmacy.  The  lac, 
when  sent  to  market,  often  contains  the  eggs  of  the  insect,  and  is 
called  "  seed-lac." 

The  lac  secretion  is  dissolved  from  the  twigs  and  branches  of  the 
tree  in  hot  water,  the  solution  is  then  evaporated  on  hot  revolving 
cylinders,  or  in  shallow  pans,  then  scraped  off  in  the  form  of  thin  sheets, 
broken  up,  and  forms  the  commercial  shellac,  graded  generally  as 
D.  C.  (dark  colored),  L.  C.  (light  colored),  B.  (bleached),  etc. 

The  coarse  qualities  of  the  melted  lac,  when  dropped  into  rounded 
pieces  1  to  1J  inches  in  diameter,  are  called  "button-lac,"  and  when 
in  larger  pieces  are  known  as  sheet-lac  or  "  piece-lac." 

The  best  quality  is  kusum-lac,  from  the  kusum  tree  (Schleichera- 
trijnga),  which  lasts  about  ten  years  after  being  stung.  The  twigs 
from  this  tree  are  of  a  light-golden  color  and  furnish  the  orange  shellac ; 
coming  principally  from  Siam.  The  second  quality  is  furnished  by 
the  dhak  or  palas,  from  the  Butea  frondosa.  The  third  quality  is 
the  piped j  from  the  Fiscus  religiosa.  All  of  the  lac-trees  except  the 
kusum  live  only  from  two  to  three  years  after  being  stung  by  the 
insect.  Commercial  shellacs  are  extremely  variable  in  quality  and 
price.  The  best  grade  of  fine  Orange  D.  C.  lac  brings  £10  12s.  per 
cwt.  in  London;  "Native  Orange,"  £8  9s.  per  cwt.;  "Garnet/! 
£7  8s.;  "Native  leaf"  and  "Button,"  £3  8s.  to  £3  6s. 

The  composition  of  shellac  is  given  by  Mr.  Halstead  *  as 


Stick-lac. 

Seed-lac. 

Shellac. 

Resin 

68  00  per  cent. 

88  .  50  per  cent. 

90  .  90  per  cent. 

Coloring-matter     .    . 

10.00    "       " 

2.50            " 

0.50     '       " 

Wax                    

6.00    "      " 

4.50 

4.00     '       " 

Gluten  

5.50    "       " 

2.00            " 

0.00     '      " 

Extraneous  and  nitrog- 
enous substances.  .  . 
Loss  

6.50    "      " 
4.00    "      " 

1.00 
1.50 

2.80     '      " 
1.80     '      " 

100.00  per  cent. 

100.00  percent. 

100.00  percent. 

*  Geo.  Watts's  Dictionary  of  the  Economic  Plants  of  India.     Government 
Printing-office,  Calcutta,  1889. 


FOSSIL  RESINS  AND  SHELLAC.  115 

A  more  complete  analysis  by  Dr.  Johns  *  shows  that  120  parts  of 
stick-lac  consist  of 


An  odorless  common  resin    

80.00  pa 
20.00 
4.50 
3.00 
0.50 
0.75 
3.00 

2.50 
1.25 
0.75 
3.75 

rts 

4.  resin  insoluble  in  ether  

Coloring-matter  analogous  to  cochineal 

Bitter  balsamic  matter  

Dun-colored  extract                                        ... 

Acia  (laccic  acid)                                    •        . 

Fatty  matter  like  wax                        

Skins  of  the  insect  and  coloring-matter  (the  latter  furnishing 
food  for  the  grub  when  hatched) 

Salts             .                             

Earths  

Loss         

120.00     " 

Shellac  dissolves  readily  in  alcohol,  benzine,  muriatic  and  acetic 
acids,  but  not  in  concentrated  sulphuric  acid.  It  dries  solely  by  the 
evaporation  of  the  solvent,  leaving  the  thin  film  unchanged,  the 
only  use  of  the  solvent  being  to  spread  the  varnish.  When  alcohol 
is  used  as  the  solvent,  the  varnish  can  be  spread  over  damp  surfaces, 
as  the  alcohol  will  take  up  the  moisture  without  much  apparent 
injury  to  the  coating,  though  >this  will  be  longer  in  drying,  as  the 
water  must  be  evaporated  with  the  alcohol. 

Shellac  can  be  applied  to  ferric  surfaces,  and  in  under- water  (fresh) 
exposures  it  generally  will  remain  about  two  years  without  any  great 
deterioration.  In  salt  water,  however,  it  will  not  stand  a  week,  and 
when  exposed  to  the  sun  and  air,  will  be  destroyed  in  about  a  month. 

Each  of  the  fossil  resins  represents  a  class  that  have  many  varieties, 
but  none  of  them  are  coniferous.  The  latter  class  are  those  that 
furnish  the  turpentine  and  common  resins  of  the  present  day,  which 
are  of  the  least  value  of  any  of  the  resins  for  a  straight  varnish  or  a 
pigment  varnish.  Their  use  in  a  varnish  is  principally  on  account 
of  their  cheapness  and  the  slightly  improved  brightness  they  confer. 

Records  of  the  protective  nature  of  some  of  these  varnish  paints 
show  that  a  suitable  combination  of  linseed-oil  and  a  resin  is  a  better 
protective  vehicle  than  oil  alone,  yet  the  smaller  the  proportion  of 
the  common  class  of  resins,  the  more  durable  was  the  coating. 

In  the  oil  and  varnish  trade,  the  essential  differences  in  the  quality 
of  varnishes  are  due  to  the  kinds  of  resin  used,  the  proportion  and 
quality  of  oil,  and  the  care  exercised  in  compounding  them  under  the 

*  Ures's  Dictionary  of  Arts  and  Manufactures. 


116  FOSSIL  RESINS  AND   VARNISHES. 

influence  of  a  well-regulated  long-heating  process.  The  temperature 
and  length  of  exposure  to  it  necessarily  varying  with  the  different 
compositions  and  quality  of  the  varnish  required  to  meet  the  condi- 
tions to  which  it  is  to  be  subjected.  Heats  approximating  the  charring- 
point  of  the  oil,  450°-500°  F.,  are  necessary  for  a  thorough  blending. 

Varnishes  and  varnish  paints  dry  better  if  moderately  warm 
when  applied,  or  if  applied  to  a  warm  surface.  Manufacturers  of 
pianos  and  other  highly  finished  surfaces  on  wood  subject  their  work 
to  200°  to  250°  F.  to  aid  the  drying  and  to  harden  the  coating. 

But  cheaper  materials  and  processes  than  the  above  are  employed 
to  produce  coatings  to  compete  with  the  basic  metal  pigments  for  use 
on  ferric  bodies.  This  careless  compounding  has  resulted  in  lowering 
both  the  price  and  quality  of  varnish  paints,  until  many  of  the  com- 
mercial varnishes  fall  below  the  average  of  the  better  class  of  straight 
pigment  oil  paints  for  protective  coatings  on  ferric  structures. 

For  trade  convenience,  100  pounds  of  resin  are  taken  for  the  unit 
of,  composition,  and  with  this  unit,  8,  10,  20,  or  any  number  of  gallons 
of  oil  rated  at  7.8  to  8  pounds  per  gallon,  are  compounded  for  the 
different  grades  of  varnish,  known  as  8,  10,  12,  etc.,  gallon  varnishes. 
To  designate  the  kind  of  resin  used,  the  initial  letter  of  the  kind  of 
resin  that  is  employed  is  taken,  viz. :  An  8Z  varnish  means  an  8-gallon 
Zanzibar;  an  8M,  an  8-gallon  Manila,  and  so  on,  both  for  the  single 
letters  or  with  a  combination  of  the  letters. 

In  the  color  varnishes  or  so-called  enamel  or  paint  varnishes, 
where  the  pigments  are  ground  in  the  selected  brand  of  varnish 
employed  for  the  vehicle,  the  designated  letter  of  the  resin  in  it  is 
generally  lost  or  withheld,  except  as  specially  furnished  by  the 
manufacturer. 

All  of  these  varnishes  or  paints  are  best  thinned  with  turpentine 
to  the  proper  consistency  required  for  the  brush.  It  is  better  for 
this  purpose  than  oil.  The  heating  of  the  oil  and  resin  together  for 
the  varnish  has  so  thoroughly  incorporated  them,  that  no  free  oil  is 
present  to  exert  any  change  or  action  in  the  drying  process,  separate 
from  that  present  in  the  coating  as  a  whole,  and  which  the  addition 
of  free  oil  as  a  thinner  would  disturb. 

Benzine,  or  other  distilled  hydrocarbon  liquid,  should  never  be 
used  in  the  composition  of  varnish  or  varnish  paint.  Their  quick 
evaporation  results  in  making  the  coating  porous,  and  liable  to 
"check"  or  " alligator,"  as  painters  term  it. 


FOSSIL  RESINS,  QUALITIES  OF,  117 

An  essential  point  in  either  a  straight  or  a  pigment  varnish "  is 
that  the  linseed-oil  should  be  made  from  ripe  seeds,  cold  pressed,  and 
be  well  aged,  and  its  "  Mucossities "  or  non-drying  elements  (nearly 
6  per  cent  of  it)  should  be  removed,  in .  part  at  least,  or  so  changed 
in  character  as  not  to  be  readily  decomposed  in  the  natural  oxida- 
tion of  the  vehicle  in  the  process  of  drying.  u 

Dingles's  Journal  reports  the  experiments  of  Dr.  Sace  (Nurem- 
berg) to  ascertain  the  nature  of  different  resins,  viz.:  Amber,  copal, 
common  resin,  dammar,  elemni,  caramba  wax,  mastic,  shellac,  and 
sandarach.  All  of  them  were  reducible  to  a  powder  form.  Amber, 
elemni,  mastic,  shellac,  and  sandarach  became  pasty  before  melting, 
the  others  became  liquid  at  once.  Amber  and  dammar  did  not  dis- 
solve in  alcohol.  Copal  became  pasty,  elemni  and  zaramba  wax  dis- 
solved with  difficulty,  while  common  resin,  mastic,  shellac,  and  san- 
darach dissolved  easily.  Caustic  soda  dissolved  shellac  readily 
common  resin  partially,  but  had  no  influence  on  the  other  resins. 

Oil  of  turpentine  dissolved  neither  amber  nor  shellac;  it  swelled 
copal,  dissolved  caramba  wax,  common  resin,  dammar,  elemni,  and 
sandarach  easily,  and  mastic  very  readily. 

Boiling  linseed-oil  had  no  effect  on  amber,  caramba  wax,  copal, 
elemni,  or  shellac,  while  sandarach  dissolved  slowly;  common  resin, 
dammar,  and  mastic  dissolved  easily  in  it. 

Petroleum  ether  had  no  effect  on  amber,  copal,  and  shellac,  and 
was  a  poor  solvent  for  caramba  wax,  common  resin,  elemni,  and 
sandarach,  and  was  a  very  good  solvent  for  dammar  and  mastic. 

Benzol  dissolved  common  resin,  dammar,  and  mastic  very  easily, 
elemni  and  sandarach  to  a  limited  extent,  caramba  wax  more  readily 
than  elemni,  but  had  no  effect  upon  amber,  copal,  and  shellac. 

Though  gums  and  resins  are  generally  spoken  of  as  belonging  to 
the  same  class,  they  are  distinguished  from  each  other  by  the  solu- 
bility of  the  gums  in  water  and  the  insolubility  of  the  resins  in  the 
same  liquid.  The  gums  are  insoluble  in  alcohol,  while  the  resins  are 
soluble  in  it.  The  so-called  gum-resins  are  soluble  in  both  water 
and  alcohol. 

The  Trades  Journal  Review  (London),  Dec.  4-14,  1901,  p.  15, 
announces  the  discovery  by  Dr.  Kronstein  (Hamburg,  Germany)  of 
the  "  Synthetical  Formation  of  Varnish  Gums  and  Resins."  These 
synthetical  products  are  identical  in  physical  and  chemical  properties 
with  those  occurring  in  nature.  The  discovery  includes  that  of  an 


118  FOSSIL  RESINS,  QUALITIES  OF. 

intermediate  product  between  the  gums  and  resins,  which  invariably 
consists  of  twelve  molecules,  affiliating  with  "linoxin,"  the  highest 
oxidation  of  linseed-oil.  Dr.  Kronstein  produces  an  artificial  resin 
identical  with  fossil  amber,  both  in  color  and  hardness;  also  has 
advanced  his  theory  and  process  by  producing  the  soft  resins  and 
balsams. 


CHAPTER  XI. 

BAKED-JAPAN    COATINGS. 

FOR  special  locations  and  ferric  constructions,  viz.:  riveted-steel 
water-pipe  lines,  anchor-  and  eye-bars,  lattice- trusses,  posts  and  beams, 
covering-  or  buckle-plates  walled  in  or  buried  in  masonry,  and  inac- 
cessible for  inspection,  repairs,  or  repainting,  a  special  coating  called 
"baked  japan"  is  being  tested  in  a  number  of  locations,  the  most 
prominent  of  which  is  a  number  of  miles  of  steel  water-pipe  mains, 
30  to  50  inches  in  diameter,  riveted  into  a  continuous  length. 

The  process  of  manufacture  and  composition  of  the  japan  is  simi- 
lar to  the  black-varnish  products,  but  a  larger  quantity  of  asphaltum, 
gilsonite,  and  other  cheaper  grades  of  gums  and  resins  replaces  the 
finer  qualities  of  fossil  and  other  resins.  It  is  applied  by  immersing 
a  hot  pipe  or  other  article  in  a  hot  bath  of  the  compound,  and  upon 
removal  from  the  bath  and  draining,  baking  it  for  a  regulated  period 
in  an  oven  or  muffle  kept  at  an  even  temperature  of  350°  to  500°  F., 
according  to  the  size  of  the  object  to  be  coated,  the  composition  of 
the  japan,  and  the  service  required  of  the  coating. 

It  fills  all  small  interstices  in  the  object,  is  elastic,  will  follow  with- 
out strain  all  changes  in  temperature  of  the  body  coated,  is  perfectly 
impervious  to  atmospheric  influences,  running  water,  brine,  acid, 
and  alkaline  and  sulphur  solutions,  that  affect  the  ordinary  oil-paint 
coatings.  Its  cost  per  square  yard  of  coated  surface  is  naturally 
much  greater  than  any  brush  coating,  and  will  vary  according  to  the 
conditions  of  its  application.  Its  durability  or  life  may  be  anywhere 
from  ten  to  fifty  times  that  of  the  ordinary  oil-paint  coating  exposed 
to  the  same  influences. 

The  composition  of  such  baked  coatings  (and  there  are  scores  of 
them  in  practical  use)  appears  to  be  of  less  importance  than  their 
proper  proportion,  and  the  care  used  in  their  combination,  applica- 
tion, and  final  baking.  It  is  reasonable,  however,  to  expect  that  a 
compound  that  requires  a  high  temperature  to  apply  and  to  harden  it 
will  be  durable,  for  the  change  induced  by  the  heat  in  the  final  dry- 

119 


120  BAKED-JAPAN  COATINGS. 

ing  of  the  coating  is  not  alone  that  due  to  evaporation,  but  is  a  thermo- 
chemical  one,  that  may  be  supposed  will  strongly  resist  any  influ- 
ences tending  to  produce  any  other  change  than  is  subordinate  to 
the  original  one  that  dried  the  coating. 

Baked-japan  coatings,  from  the  nature  of  their  ingredients,  are 
electrically  passive,  except  to  currents  of  high  potential;  hence  it 
remains  for  time  to  determine  whether  the  stray  electric  currents, 
now  a  fruitful  source  of  electrolysis  in  all  ferric  bodies  that  lie  in  the 
pathway  of  their  return  to  their  place  of  generation,  will  not  find  the 
rows  of  rivets  that  unite  the  several  sections  of  the  underground 
water-pipe  lines  coated  with  baked  japan,  the  points  to  concentrate 
the  electrolytic  energy  for  a  rapid  corrosion  of  the  pipe  system  at 
thousands  of  points  in  each  mile,  instead  of  a  hundred  or  so,  exposed 
in  the  usual  spigot  and  bell  method  of  joining  the  pipes.  The  elec- 
trolytic action  at  the  rivets  will  be  hastened  by  the  difference  in  poten- 
tial between  the  rivets  and  the  pipe-metal — both  of  whi^h  are  of 
different  potential  from  the  japan  coating.  The  brush-paint  coating 
applied  to  the  rivet-heads  will  afford  but  little  if  any  protection  against 
corrosion  or  electrolytic  action,  as  they  will  take  place  underneath 
the  coating,  and  will  require  but  a  small  development  of  either  before 
they  cast  off  the  paint  and  have  an  easier  field  for  their  progress. 

Another  source  of  corrosion  which  these  joints  can  resist  but  a 
short  time  is  the  action  of  the  acid  elements  present  in  all  earths.  In 
the  case  of  these  water-pipe  lines  exposed  for  miles  to  a  great  number 
of  strong  electric  currents,  the  ordinary  rate  of  corrosion  from  earth 
and  water  will  be  intensified,  as  in  the  water-tower  stand-pipe  case 
cited  in  Chapter  XXXIV  of  this  volume. 

While  the  baked- japan  coating  of  itself  leaves  but  little  if  any 
room  for  improvement  in  the  coating  of  water-mains,  it  will 
surely  be  a  source  of  future  regret  that  a  better  method  of  joining 
the  short  sections  of  pipe  into  a  continuous  line  was  not  adopted  than 
the  riveted  joints  thus  far  used. 

If  the  brush  or  modified  japan  coating  applied  to  the  pipe  circular 
seams  is  adequate  for  their  permanent  protection  from  corrosion, 
why  incur  the  expense  of  a  baked  coating  for  the  body  part  of  the 
pipe?  If  it  is  not  a  permanent  protection  for  them,  then,  as  a  chain 
is  no  stronger  than  its  weakest  link,  there  must  be  a  great  number  of 
weak  links  in  this  method  of  constructing  and  protecting  water-pipe 
mains  that  ought  not  to  be  repeated. 

The  interruption  of  the  water-supply  of  a  large  city  is  too  serious  a 


BAKED-JAPAN  COATINGS.  121 

matter  to  allow  the  question  of  a  few  hundred  dollars  a  mile  differ- 
ence between  a  good  and  a  bad  plan  of  joint  construction  to  be  a  factor 
in  determining  which  to  use.  That  a  number  of  American  cities 
have  this  bad  joint  is  evidenced  from  trade  catalogues  and  other 
illustrations  of  this  method  of  constructing  large  water-supply  pipe- 
lines. 

The  question  has  been  raised  as  to  whether  the  baking  of  the 
coating  effects  a,ny  further  chemical  union  between  the  oil  and  the 
other  constituents  of  the  dip,  other  than  that  developed  in  the  process 
of  manufacture?  It  is  probable  that  it  does,  as  the  baking  tempera- 
ture is  materially  higher  than  that  in  the  process  of  manufacture. 
The  pipe-coating  material  before  baking  is  readily  soluble  in  turpen- 
tine, but  after  baking  is  not  softened  by  prolonged  digestion  in  hot 
turpentine,  and  but  indifferently  in  hot  naphtha.  The  preliminary 
heating  of  the  pipe  before  immersion  in  the  hot-pipe  dip  assures  its 
adhesion  and  impermeability,  as  the  air  and  moisture  are  practically 
excluded  and  the  preliminary  bond  of  the  coating  to  the  metal  is 
perfect.  The  evaporation  of  the  volatiles  in  the  japan  dip  in  the 
process  of  baking  is  so  quickly  effected  in  the  earlier  stage  of  baking, 
that  the  liquid  or  fused  mass  of  the  resins  readily  replaces  them  and 
fills  the  interstices  caused  by  their  evaporation,  and  ensures  a  smooth 
unbroken  surface  to  the  coating  altogether  different  from  that  of  a 
dried  paint. 

The  so-called  japanned  or  enamelled  coatings  used  on  sewing- 
machines  and  many  domestic  machines  and  utensils  are  generally 
of  that  composition  that  will  give  the  best  appearance.  They  are 
not  proof  against  corrosion  under  many  exposures  that  would  be 
resisted  by  a  good  varnish  coating  or  an  earthenware  salt  glaze.  As 
a  rule  they  chip  easily,  and  corrosion  once  established  in  these  spots, 
spreads  rapidly  beneath  the  enamel  and  flakes  it  off. 

A  properly  made  enamel  is  essentially  a  glaze,  similar  in  com- 
position and  properties  to  glass,  and  has  all  of  the  advantages  and 
disadvantages  of  that  substance.  It  is  melted  at  a  high  heat,  1200° 
to  1400°  F.,  and  adheres  to  the  surface  of  metals  perfectly.  Enamels 
generally  resist  the  action  of  acid  solvents,  but  are  brittle  and  easily 
chipped  off. 

"  The  best  baked  japans  are  intermediate  between  enamels  and 
ordinary  varnishes,  and  resist  the  action  of  solvents  almost  as  well  as 
an  enamel,  while  they  surpass  the  latter  in  the  tenacity  of  the  coating, 
allowing  the  metal  they  cover  to  be  bent  to  a  moderate  degree  without 


122  BAKED-JAPAN  COATINGS. 

injury,  while  their  elasticity  is  generally  greater  than  a  hard  varnish. 
In  hardness,  baked  japan  is  intermediate  between  varnish  and  glass, 
or  harder  than  gypsum  and  nearly  as  hard  as  marble."  * 

Baked  black  japans  are  made  from  linseed-oil  and  asphalt  as  a 
base,  mixed  with  more  or  less  copal  resins,  usually  kauri,  and  are 
thinned  with  turpentine.  Like  varnishes,  the  more  linseed-oil  they 
contain  and  the  less  driers  (oxides  of  lead  and  manganese)  the  more 
durable  they  are ;  but  to  get  them  to  bake  hard  at  a  comparatively 
low  heat,  the  proportion  of  oil  is  frequently  decreased  as  much  as 
possible  and  the  amount  of  driers  increased,  forming  an  inferior, 
brittle  coating  easily  injured  by  a  slight  blow  or  rough  handling. 

Modern  baked- japan  water-pipe  coatings  are  very  similar  in  char- 
acter and  in  their  application  to  Dr.  Angus  Smith's  anti-corrosive 
water-pipe  coating,  that  forms  the  subject  of  the  following  chapter. 

*  "Paints,  Varnishes,  and  Enamels."     A.  H.  Sabin,  M.S.,  New  York,  1896 


CHAPTER  XII. 

DR.  ANGUS  SMITH'S  ANTI-CORROSIVE  WATER-PIPE  AND  OTHER  COATINGS. 

THIS  compound  was  originally  applied  by  Dr.  Smith  in  1840,  and 
patented  in  England  in  1850,  and  was  first  used  in  America  in  1858 
upon  some  pipes  imported  from  Glasgow.  Dr.  Smith's  original  for- 
mula is  not  definitely  known.  Mr.  James  P.  Kirkwood's  Report  on 
the  Brooklyn  Water  Works,  published  in  1858,  gave  the  following 
formula  for  it,  and  it  was  used  to  some  extent  upon  the  pipes  for 
those  works;  evidently  satisfactorily,  for  Mr.  Peter  Milne,  engineer 
in  charge  of  the  extension  of  the  works,  reports:  "That  36-inch  pipe- 
mains  laid  for  35  years  were  found  to  be  in  perfect  condition  exter- 
nally, and  but  few  tubercules  or  other  deposits  were  found  on  the 
inside  of  pipes."  The  pipes  had  been  coated  by  heating  them  in  an 
open  furnace  to  about  500°  F.,  and  then  immersing  them  in  a  bath 
formed  from  coal-tar,  as  follows:  * 

Coal-tar  was  distilled  until  the  naphtha  was  removed  and  the 
material  deodorized  and  of  the  consistency  of  melted  wax  or  a  thick 
molasses.  This  process  also  eliminated  most  of  the  tarry  acids,  and 
necessarily  required  considerable  time  and  care  to  effect.  Five  to 
6  per  cent  and  in  some  cases  8  per  cent  of  pure  raw  linseed-oil 
was  then  added  and  stirred  in  well.  The  bath  was  made  deep  enough 
to  receive  the  pipes  when  placed  in  it  vertically.  The  pipes  remained 
in  the  bath  until  they  had  cooled  down  to  the  same  temperature, 
about  300°  F.,  or  about  30  minutes  for  a  20-inch-diameter  pipe. 
Careful  attention  was  given  to  the  length  of  time  the  pipes  were 
to  remain  in  the  bath.  A  less  time  than  30  minutes  for  a  20-inch 
pipe  gave  an  unsatisfactory  result.  For  pipes  from  4  to  12  inches 
in  diameter,  15  to  20  minutes'  immersion  appeared  to  be  sufficient 
to  get  a  reliable  coating. 

When  the  coal-tar  was  distilled  to  the  consistency  of  mineral 

*  "  Report  in  relation  to  Proposals  made  by  various  parties  to  protect  the 
cast-iron  water-pipes  of  the  City  of  Brooklyn  from  corrosion."  By  James  P. 
Kirkwood,  Chief  Engineer.  City  Document,  published  by  Hosford  &  Co.,  1858. 

123 


124     DR.  SMITH'S  ANTI-CORROSIVE  WATER-PIPE  COATING. 

pitch  or  bitumen,  or  when  common  resin  or  Burgundy  pitch  was 
mixed  with  it  and  used  as  a  bath,  the  pipe  coatings  became  hard  and 
brittle  when  cold,  and  the  bath  material  would  not  answer,  even 
where  the  quantity  of  linseed-oil  used  in  it  was  increased  to  15  or 
more  per  cent. 

The  preliminary  heating  of  the  pipes  to  500°  F.  before  immersion 
in  the  bath,  after  a  short  experience,  was  found  to  be  prejudicial, 
and  was  abandoned.  The  combustion  gases  of  the  heating-furnace 
that  were  deposited  on  the  pipes  appeared  to  affect  the  bonding 
of  the  coating  to  the  pipe-metal,  and  the  pipes  when  removed  from 
the  bath  were  not  satisfactory,  and  new  specifications  for  coating 
them  were  adopted. 

These  specifications  required  the  same  preparation  of  the  coal-tar 
for  the  bath  as  given  above,  and  for  it  to  be  kept  at  a  temperature  of 
300°  F.  during  the  period  of  dipping.  As  the  material  was  continu- 
ally deteriorating  during  the  dipping  process,  fresh  material  was  to 
be  added  frequently,  and  at  least  8  per  cent  of  linseed-oil,  as  near  as 
could  be  guessed  at,  kept  in  the  bath,  or  added  with  the  fresh  pitch. 
The  bath  was  required  to  be  occasionally  entirely  emptied  of  its  con- 
tents and  to  be  refilled  with  new  material.  The  old  material  after 
a  few  days'  use  was  found  to  be  hard  and  brittle  like  common  pitch. 

Every  pipe  was  immersed  cold,  but  not  frosty,  and  was  to  remain 
in  the  bath  until  it  had  attained  the  temperature  of  the  bath,  300°  F. 
This  period  was  about  30  minutes  for  the  20-inch  pipe,  as  in  the  pre- 
vious specification.  It  required  a  brisk  fire  to  be  maintained  under  the 
bath  to  overcome  the  cooling  action  of  the  cold  pipe  when  immersed. 

The  presence  on  the  pipe  of  moulding-sand,  dirt,  moisture,  frost, 
or  oil  and  grease  of  any  kind,  was  found  to  be  detrimental  to  the  appli- 
cation of  the  coating,  and  their  removal  was  necessary  before  dipping. 

The  royalty  paid  Dr.  Smith  for  the  use  of  his  formula,  although  no 
United  States  patent  was  in  effect,  was  37J  cents  per  ton  of  pipe. 

The  price  paid  the  English  pipe-founders  for  coating  the  pipes 
ordered  from  them  by  the  Brooklyn  Water  Works  was  $1.25  per 
ton,  for  the  years  1858  to  1860.  American  pipe-founders'  and  con- 
tractors' price  for  Dr.  Smith's  coating  was  about  $3.00  per  ton  as 
against  a  plain  asphalt  coating  of  $1.83  to  $2.25  per  ton. 

The  efforts  of  other  water-works'  engineers  to  follow  Dr.  Smith's 
formula,  and  possibly  to  improve  or  cheapen  its  application,  resulted 
in  so  great  a  variety  of  recipes  and  consequently  inferior  results,  that 
but  little  dependence  can  be  placed  upon  their  reports.  The  tern- 


DR.  SMITH'S  ANTI-CORROSIVE  WATER-PIPE  COATING.     125 

perature  of  the  preliminary  heating  of  the  pipe  before  immersion 
varied  from  200°  to  700°  F.,  and  the  proportion  of  ingredients  and 
their  composition  was  equally  startling,  as  were  also  the  attending 
results. 

Mr.  Chas.  Harmony,  Chief  Engineer  of  the  Louisville,  Ky.,  Water 
Works,  who  experimented  for  a  number  of  years  with  Dr.  Smith's 
formula  as  given  by  Mr.  Kirk  wood,  reports:  That  "some  of  the  pipes 
so  coated,  after  an  exposure  of  from  six  to  eighteen  years,  were  in 
as  perfect  condition  as  when  first  laid;  but  it  was  an  exception,  not 
a  rule.  In  a  majority  of  cases  the  coating  on  the  inside  of  the  pipe 
was  all  gone,  and  upon  the  outside  surfaces  it  had  apparently  been 
of  no  importance  in  prolonging  the  life  of  the  pipe.  The  difficulty 
experienced  was,  that  in  the  heating  of  the  bath  to  the  temperature 
of  300°  F.,  the  coal-tar,  resin,  and  pitch  compounds  became  unman- 
ageable by  approximating  the  condition  of  boiling  and  volatilization, 
and  going  everywhere  except  in  the  place  it  was  wanted.  The  coat- 
ing was  thick  and  apparently  unbroken,  but  exceedingly  brittle, 
and  would  crack  and  scale  off  in  the  ordinary  process  of  handling." 

The  tension  of  coal-tar  and  pitch  at  a  temperature  of  300°  F.  is 
hardly  less  than  that  of  water  at  the  same  heat,  or  equal  to  about  53 
pounds'  pressure.  To  maintain  such  a  temperature  in  the  bath  in 
open  atmospheric  pressure  is  impractical,  and  the  composition  becomes 
unmanageable. 

Other  engineers  report  that  the  pipes  after  twenty  years  of  expo- 
sure were  found  to  be  free  from  corrosion,  but  the  coating  had  lost  its 
bond  to  the  pipe,  and  evidently  remained  in  place  because  corrosion  or 
other  causes  had  not  developed  enough  energy  to  cast  it  off  against 
the  pressure  of  the  surrounding  earth. 

In  these  and  similar  instances  of  failure,  the  results  appear  to 
have  been  more  markedly  against  pipes  cast  in  greensand  instead 
of  a  dry  sand  or  loam-mould,  evidently  because  the  thick,  vitreous, 
or  partly  fused  greensand  coating  carried  so  much  air  in  its  rough, 
sandy  surface  into  the  bath,  that  it  could  not  escape  through  the 
heavy  pitch  composition.  Furthermore,  this  varnish  itself  was  over- 
charged with  its  own  vapors  under  tension,  and  of  greater  density 
than  the  air,  and  confined  them  until  the  cooling  of  the  pipe  when 
removed  from  the  bath  rendered  their  escape  impossible,  hence  the 
irregularity  in  the  results.  Had  the  pipes  been  baked  in  an  oven 
after  removal  from  the  bath,  as  in  some  recent  applications  of  this 
compound,  the  rough,  vitreous  sand  coating  on  the  pipes  doubtless 


126  COAL-TAR  COATINGS. 

would  have  ensured  a  more  enduring  coating  than  the  same  com- 
pound applied  to  a  smooth,  dry-sand  moulded  surface,  or  one  of  rolled 
wrought  iron  or  steel.  This  silicate  coating  would  be  reinforced  by 
the  tough  Bower-Barff  skin,  to  which  it  is  naturally  so  closely  attached 
as  to  require  pickling  to  remove.  It  is  the  subsequent  baking  that 
the  pipe  receives  that  renders  this  process  a  success.  The  composi- 
tion of  the  bath  can  be  varied  greatly  without  much  detriment  to 
the  protective  nature  of  the  coating,  if  the  baking  process  follows 
the  bath. 

The  generally  unfavorable  results  attendant  on  the  use  of  Dr. 
Smith's  formula  without  the  baking  process,  and  the  care  and  cost 
of  it,  determined  the  present  practice  of  the  pipe-founders,  which  is 
to  place  the  pipes  for  a  short  time  in  an  oven  heated  to  250°  to  300°  F., 
then  immerse  them  in  the  bath  of  hot  coal-tar  and  pitch,  and  then 
cool  them  in  the  open  air. 

This  coating  is  one  of  appearance  more  than  of  a  protective  or  an 
enduring  nature,  and  is  only  applicable  to  water-pipes,  as  in  gas-pipes 
so  treated  the  solvent  action  of  the  hydrocarbon  vapor  soon  removes 
the  coating,  and  the  joints  draw  and  leak  worse  than  with  the  uncoated 
surfaces. 

The  careless  and  indifferent  boiling  of  coal-tar,  to  free  it  from 
its  many  acid  and  other  impurities,  makes  it  a  variable  and  unsatis- 
factory coating.  Lime,  gypsum,  and  other  mineral  substances  mixed 
and  boiled  with  the  coal-tar  to  neutralize  the  ammonia,  acids,  sulphur, 
etc.,  only  render  the  tar  more  unreliable  and  unmanageable.  The 
careless  heating  of  the  pipes  and  bath,  also  the  length  of  time  the 
pipes  are  left  in  the  bath,  and  the  subsequent  treatment  of  the  pipes 
when  removed,  are  all  factors  in  the  indifferent  results  obtained. 

Unless  great  care  is  exercised  the  small  pipes  will  be  overheated 
and  unequally  coated  and  brushed  off,  inside  and  outside.  The  larger 
pipes,  requiring  a  longer  time  to  heat,  from  the  mass  of  metal  they 
contain,  will  be  underheated  in  the  oven  and  cool  down  the  bath 
to  a  lower  degree  than  is  requisite  for  a  reliable  coating.  The  subse- 
quent brushing  of  the  coating,  both  inside  and  outside,  during  the 
first  period  of  cooling  (a  matter  of  from  30  minutes  to  2  hours), 
promotes  its  reliability. 

All  coal-tars  or  their  compounds  of  whatever  nature  used  as  a 
bath,  or  applied  with  a  brush  to  any  surface,  hot  or  cold,  are  subject 
to  the  law  of  fractional  distillation;  that  is,  that  such  a  mixture  during 
the  process  of  distillation  remains  at  the  boiling-point  of  that  constitu- 


DEAD  OIL  IN  PIPE  COATINGS.  127 

ent  which  boils  at  the  lowest  temperature  until  that  constituent  is 
exhausted,  then  changes  to  the  next  boiling-point,  and  remains  there 
for  a  time,  and  so  on. 

The  low  boiling-  or  evaporating-point  of  the  lighter  elements  of 
coal-tar  or  petroleum  products  makes  them  very  uncertain  in  their 
composition,  as  changes  of  temperature  in  the  bath  from  220°  to 
350°  F.  are  frequently  noted  without  any  change  in  the  character  of 
them  that  the  eye  can  detect. 

The  character  of  the  bath  composition  changes  so  continuously 
and  rapidly  during  the  dip  that  frequent  additions  of  fresh  stock 
must  be  made.  These  necessarily  cool  the  bath,  change  its  composi- 
tion, and  irregular  coatings  ensue  to  that  extent  that  an  entirely 
new  bath  is  necessary. 

The  use  of  linseed-oil  with  coal-tar  for  pipe  coatings,  as  usually 
applied  at  the  pipe-foundries,  is  of  very  uncertain  value.  It  causes 
the  dip  compound  to  froth  to  nearly  double  its  volume,  and  renders 
the  coating  lumpy  in  appearance  and  uncertain  in  its  bond  to  the 
pipe-metal.  It  requires  some  effort  by  continual  stirring  to  incor- 
porate it  with  the  coal-tar  and  pitch,  and  it  is  always  liable  to  separate 
from  them  and  float  upon  the  surface,  froth,  soften  the  coating,  and 
delay  its  drying. 

Dr.  Angus  Smith  evidently  used  a  number  of  formulae  for  pipe 
coatings  that  contained  linseed-oil  as  one  of  the  ingredients.  A  long 
line  of  careful  experiments  with  the  best  of  coal-tar,  pitch,  and  linseed- 
oil  carefully  heated  and  applied,  gave  almost  uniformly  good  coatings. 
Using  the  commercial  grades  of  these  substances  and  having  the 
ordinary  day  laborer  to  compound  and  apply  them,  the  result  was 
necessarily  inferior,  so  much  so  as  to  cause  the  abandonment  of 
linseed-oil  in  coal-tar  pipe  coatings  by  modern  founders.  If,  how- 
ever, the  truth  were  acknowledged,  the  present  coal-tar  pipe  coating 
would  be  found  to  be  living  on  the  well-earned  and  deserved  reputa- 
tion of  Dr.  Smith's  compound. 

Dead  Oil  in  Pipe  Coatings. 

That  part  of  coal-tar  obtained  in  the  fractional  distillation  of 
the  tar  between  the  temperatures  of  410°  to  750°  F.,  and  which  con- 
tains creosote  and  anthracine  oils  (see  Analysis,  Chapter  IX),  .is 
used  to  keep  the  pipe  dip  at  a  standard  quality.  It  evaporates  by 
itself,  about  one-seventh  as  rapidly  as  water,  when  both  are  at  atmos- 
pheric temperature. 


128  DEAD  OIL  IN  PIPE  COATINGS. 

One  part  of  dead  oil  to  about  seven  parts  of  coal-tar  increases 
the  proportion  of  the  heavy  oils  in  the  tar  dip  from  about  25  to  35 
per  cent,  and  appears  to  make  the  coatings  more  uniform  and  of  a 
better  character  than  where  fresh  tar  is  used  to  reinforce  the  bath. 

Thick  tar  gives  thicker  and  more  uniform  coatings  than  thin  tar, 
and  fresh  tar  requires  a  hotter  pipe  to  take  bond  than  does  old  tar. 

Crude  gas  coal-tar  boiled  from  five  to  six  hours  becomes  a  soft 
solid  at  atmospheric  temperatures.  During  the  boiling  the  tempera- 
ture remains  at  about  220°  F.  for  about  an  hour,  then  rises  to  about 
290°,  stays  there  for  a  time,  and  finally  rises  to  about  350°  F.  All  of 
the  naphtha  is  removed  and  the  tar  is  deodorized  and  reduced  to  the 
consistency  of  very  thick  molasses.  If  to  sixteen  parts  of  this  tar 
1  per  cent  of  boiled  linseed-oil  be  added,  no  frothing  occurs  even  at 
400°  F.  The  mixture  is  thick  and  does  not  harden  well  on  light 
iron  pipes  about  ^-inch  thick.  On  heavy  iron  pipes  an  inch  or  more 
thick,  the  coating  hardens  without  difficulty;  in  some  cases  becomes 
too  hard,  is  brittle,  and  flakes  off  readily  by  mechanical  injury  when 
handled.  Dead  oil  added  to  thin  the  mixture  causes  no  frothing. 
The  experiments  show  that  linseed-oil  could  be  used  with  success 
and  advantage  with  partially  refined  coal-gas  tar,  and  also  indicates 
that  its  application  requires  more  intelligent  care  than  the  methods 
employed  with  the  usual  crude  tar  coating. 

Experiments  with  a  refined  tar  containing  dead  oil  show  that  as 
high  as  8  per  cent  of  boiled  linseed-oil  resulted  favorably  in  solidity 
and  hardness  of  the  coating.  In  other  instances,  where  from  1  to 
8  per  cent  of  raw  linseed-oil  was  used  instead  of  boiled  oil,  frothing 
occurred  and  a  poor  coating  resulted,  evidently  due  to  the  presence 
and  evaporation  of  the  water  in  the  raw  oil.  There  is  about  5 
per  cent  of  water  naturally  held  in  combination  with  the  best  quality 
of  raw  linseed-oil  made  from  ripe  flaxseed,  and  nearly  8  per  cent 
in  the  oil  made  from  unripe  seed.  With  many  brands  of  commercial 
linseed-oil,  10  per  cent  additional  of  water  is  frequently  incorporated 
by  stirring  it  in  with  a  paddle  or  passing  it  through  a  mixing  mill.  All 
such  oils  are  likely  to  be  made  up  from  fish,  resin,  mineral  or  vegetable 
and  animal  oils  with  no  linseed-oil  of  any  quality  in  them,  and  all  the 
difficulties  developed  by  these  mixtures  with  the  coal-tar  are  saddled 
upon  the  scapegoat,  linseed-oil. 

Refined  coal-gas  tar  is  practically  out  of  the  market  and  has  been 
for  many  years.  What  small  amount  of  crude  coal-tar  is  available  is 
too  valuable  and  in  too  great  demand  for  the  chemical  products  in  it 


WATER-PIPE  DIPS  AND  COATINGS.  129 

to  allow  of  its  use  to  the  great  extent  that  pipe-founders  require  for 
their  work.  Heavy  roofing  pitch  alone  will  run  in  moderately  warm 
weather  and  becomes  too  soft  and  sticky  for  a  pipe  covering,  unless 
laid  immediately  after  coating.  This  is  impracticable,  and  in  cold 
weather  it  is  too  hard  and  brittle  for  transportation  or  handling. 

Nine  parts  of  heavy  roofing  pitch  with  one  part  of  boiled  linseed- 
oil  give  a  thick  glossy  coating  less  brittle  than  pitch  alone. 

Two  parts  of  boiled  linseed-oil  with  the  nine  parts  of  the  pitch 
give  a  coating  more  elastic  and  tough. 

Three  parts  of  boiled  linseed-oil  with  nine  parts  of  pitch,  the  coat- 
ing is  more  bulky  and  less  smooth  than  with  the  others,  while  with 
larger  proportions  of  the  linseed-oil  the  coating  partakes  of  the  char- 
acter of  a  slow-drying  paint  and  requires  baking,  which  gives  it  a 
superior  quality. 

Coal-gas  tar  belonging  to  the  class  of  pyrogenic  (fire-formed) 
compounds  is  unstable  at  ordinary  temperatures,  and  is  continuously 
decomposing  by  the  evaporation  of  its  many  hydrocarbon  elements, 
until  nothing  but  the  hard  friable  pitch  is  left,  which  contains  nearly 
all  of  the  sulphur  element  in  the  coal  that  forms  the  base  of  the  tar 
product.  Asphaltum,  also  a  pyrogenic  product,  formed  by  the  slow 
evaporation  or  distillation  of  petroleum,  decomposes  upon  exposure 
by  reason  of  the  oxidation  of  the  sulphur  element  in  it,  but  is  more 
durable  than  the  coal-tar  residuum  or  pitch  (asphalt). 

Asphaltum  and  linseed-oil  coatings  do  not  harden  well,  unless  a 
hard  grade  of  asphaltum  is  used. 

Water-pipe  Dips  and  Coatings. 

There  are  many  pipe  dips  upon  the  market,  some  covered  by  pat- 
ents of  doubtful  validity,  others  secret  or  proprietary  compounds  of 
doubtful  utility.  Some  of  these  compounds  appear  as  pipe  dips, 
also  as  brush  paints  applicable  for  ferric  constructions  other  than 
pipes.  (See  Paint  Tests,  Chapter  XXIX.) 

The  P.  and  B.  Pipe  Dip  is  a  patent  dip ;  the  principal  ingredients 
are  probably  an  asphalt  and  candle-tar  pitch.  The  latter  is  a  pitch 
obtained  by  the  distillation  of  animal  fats  or  refuse.  Upon  pipes  its 
coating  is  similar  to  an  asphalt  coating,  not  hard  nor  brittle,  not 
very  glossy  nor  very  tenacious. 

The  P.  and  B.  Universal  Paint  is  an  asphaltum  paint;  the 
vehicle  contains  carbon  disulphide  as  the  volatile  element,  the  evapo- 
ration of  which  is  not  only  nauseating  and  dangerous  to  all  animal 


130  WATER-PIPE  DIPS  AND  COATINGS. 

life,  but  carries  the  danger  of  explosion  and  fire  risk.  Whatever  good 
qualities  it  may  possess  when  on,  are  more  than  offset  by  the  dangers 
connected  with  its  application. 

The  P.  and  B.  "Ruberine"  consists  of  "ruberoid"  dissolved  in 
.naphtha.  " Ruberoid"  consists  of  California  asphaltum  or  maltha 
and  candle-tar  pitch  digested  and  vulcanized  with  sulphur.  "  Ru- 
berine" dries  rapidly,  is  hard  to  spread  smoothly,  but  gives  an  elastic 
or  rubbery  coating.  See  tests  of  paints,  New  York  Elevated  Railway 
Viaduct,  for  an  example  of  its  qualities. 

Mineral  Rubber  Dip  (or  Rubber  Coating)  is  a  secret  composition 
whose  appearance  indicates  that  it  is  largely  asphaltum.  It  is  rather 
duller  in  appearance  than  the  ordinary  coal-tar  or  asphalt  mixture. 
The  dip  requires  a  temperature  of  about  400°  F.  to  apply,  and  then  it 
is  almost  impossible  to  get  a  smooth  or  neat-appearing  surface.  As 
yet  its  protecting  qualities  have  not  been  determined. 

" Bitumastic"  Products  comprise  an  enamel  to  be  applied  in  a 
molten  state  to  the  metal.  Bitumastic  cement  is  used  hot  for  the 
preservation  of  ships'  bilges  and  frames,  instead  of  the  usual  hydraulic 
cement  coatings,  and  also  for  the  protection  of  water-pipes.  Bitu- 
mastic solution  has  bitumen  for  its  base.  It  is  a  brilliant  black 
paint  applied  the  same  as  other  paints,  and  is  probably  similar  in 
character  and  composition  to  "Smith's  Durable  Coating."  It  has 
been  used  to  a  considerable  extent  on  steel  water-pipes  and  for 
the  limited  period  of  test  in  that  service  is  favorably  spoken  of.  It 
dries  in  24  hours,  is  said  to  be  unaffected  by  acidulous,  alkaline, 
or  brine  solutions.  If  applied  to  the  clean  dry  surface  of  the  metal, 
does  not  crack  or  peel  when  alternately  wet  or  dry,  or  exposed  con- 
tinually to  running  water  in  penstocks,  water-wheels,  etc.  It  is 
not  affected  by  a  moderate  heat,  nor  by  sulphur  fumes,  and  is  fur- 
nished ready  for  use  at  $1.75  per  gallon.  It  is  very  volatile,  and  the 
packages  must  be  well  stirred  while  being  used.  Its  covering  power 
is  about  400  square  feet,  and  its  weight  about  9.5  pounds  per  gallon. 

(l  Crysolite"  Enamel  and  Paint.  "Crysolite"  paint  is  made  from 
oil  and  a  by-product,  oven-coke.  It  weighs  9.5  pounds  per  gallon 
and  spreads  500  square  feet  as  furnished  for  a  paint.  When  thinned 
with  12.5  per  cent  of  oil,  will  cover  1000  square  feet,  and  under  general 
conditions  in  both  hot  and  cold  weather,  dries  completely  in  30  hours. 
"Crysolite"  Enamel  is  a  quick-drying  paint  of  the  same  character  as 
the  above,  and  dries  in  one  hour.  "Crysolite"  products  are  alkaline 
in  reaction,  whereas  coal-tar  products  in  general  have  an  acid  reac- 


WATER-PIPE  DIPS  AND  COATINGS  131 

tion.  "Crysolite"  is  better  for  being  applied  warm  or  hot  (as  all 
ferric  paints  are).  In  the  winter  one-eighth  of  its  volume  of  tur- 
pentine can  be  added  to  aid  its  spreading  power,  which  can  be  made 
to  cover  from  800  to  1000  square  feet.  "Crysolite"  paints  cost 
about  75  cents  per  gallon  mixed  ready  for  summer  use. 

" Crysolite"  coatings  on  ammonia  tank-cars  and  reservoirs  stand 
the  action  of  ammonia  liquors  and  gases  better  than  most  of  the  paints 
used  for  this  purpose.  " Crysolite"  baked  coatings  under  test  re- 
sisted the  action  of  carbonate  of  ammonia  and  ammonium  chloride 
liquors  for  three  months  without  injury.  " Crysolite"  under  the 
influences  of  strong  brine  is  more  favorable  than  the  commercial 
asphaltum  or  the  ordinary  coal-tar  paints. 

Hickenloo-per's  gas-pipe-dip  compound,  used  by  the  Cincinnati 
Gas  Light  and  Coke  Company,  the  United  Gas  and  Improvement 
Company,  and  several  other  gas  companies,  to  coat  their  small  service 
pipes,  has  a  record  of  many  years'  exposure  in  the  ground  with  few 
traces  of  corrosion.  The  failures  thus  far  reported  show  that  neither 
the  process  nor  compound  were  at  fault,  but  the  lack  of  thoroughness 
and  intelligence  in  its  application.  The  pipes  are  first  cleaned  from 
rust  and  mill-scale  and  then  immersed  in  the  following  dip  and 
in  the  following  manner.  Twenty  gallons  of  retort  coal-gas  tar  are 
brought  up  to  a  boiling  heat  for  a  short  time  to  evaporate  as  much 
of  the  water,  acids,  ammonia,  etc.,  as  possible,  then  20  pounds  of 
freshly  slaked  lime  are  sifted  in  from  the  top  and  well  worked  into 
the  tar.  Boil  down  to  the  consistency  between  a  coal-tar  and  a 
pitch.  When  settled,  add  four  pounds  of  tallow  and  one  pound  of 
powdered  resin;  stir  until  all  are  dissolved  and  thoroughly  incor- 
porated, then  let  the  mass  cool  and  settle;  then  ladle  off  into  barrels. 
When  ready  for  use,  to  each  barrel  of  forty-five  gallons  of  the  above 
mixture  add  four  pounds  of  crude  india-rubber  dissolved  in  turpen- 
tine to  the  consistency  of  thick  cream.  Heat  the  mixture  to  about 
150°  F.  and  immerse  the  pipe,  previously  heated  to  about  the  same 
temperature.  After  a  few  minutes'  immersion  the  pipes  are  removed 
from  the  bath  and  laid  upon  skids  to  harden.  The  coating  is  some- 
what softer  than  the  usual  pipe-founders'  dip,  and  requires  more 
time  to  harden,  and  continues  hardening  for  a  number  of  hours  after 
cooling  down  to  atmospheric  conditions.  The  compound  is  especially 
useful  in  coating  the  screwed  ends  of  threaded  pipes.  It  is  better  for 
this  purpose  than  the  red-lead  compounds  usually  employed. 

All  rough  coatings  are  detrimental  to  the  life    of  water-pipes. 


132  WATER-PIPE  DJPS  AND  COATINGS. 

Upon  the  inside  surfaces  the  pits  or  cavities  that  constitute  the 
rough  surface  of  the  coating  are  the  first  to  catch  the  saline,  sulphur, 
or  other  impurities  in  the  water  that  form  the  basis  for  the  develop- 
ment of  the  rust  cones.  The  coating  under  these  pits  is  the  first  to 
break  down,  being  of  inadequate  thickness — probably  only  -^-J-¥  inch 
thick.  The  external  surface  of  the  pipe  is  as  rough  as  the  inside, 
and  is  not  only  exposed  to  the  moisture  to  inaugurate  corrosion, 
but  this  moisture  will  contain  all  the  acids  in  the  soil  in  which  the 
pipes  are  laid. 

In  all  cases  of  the  corrosion  of  water-pipes,  it  is  the  porosity  of 
the  coating  that  causes  the  formation  of  the  tubercles  and  decay  of 
the  pipe.  Nearly  all  of  the  dip  coatings,  when  tested  by  themselves 
or  not  in  contact  with  ferric  substances,  were  practically  uninjured 
by  acid  solutions  or  running  water. 

In  general,  all  pipe  coatings,  applied  as  they  nearly  always  are 
in  a  careless,  indifferent  manner,  will  begin  to  show  indications  of 
tubercles  in  three  years,  and  cases  of  tubercles  in  large  pipes  at  the 
end  of  sixteen  years  have  been  noted,  where  the  carrying  capacity 
of  the  pipes  had  been  reduced  20  per  cent.*  Engineers  must  earnestly 
take  up  this  question  of  reduced  carrying  capacity  of  their  water- 
pipes  and  decide  whether  it  is  not  more  economical  to  add  from  5  to 
10  per  cent  to  the  cost  of  the  pipe  in  the  form  of  better  coating  mate- 
rials and  better  methods  of  their  application  than  to  submit  to  this 
decrease  in  flow,  that  always  grows  less  with  the  age  of  the  pipe,  while 
the  demand  upon  the  service  is  always  increasing. 

Specifications  for  pipe  coatings  appear  to  be  of  little  use  in  produc- 
ing a  satisfactory  coating,  either  in  appearance  or  durability,  as  the 
directions  they  give  are  more  often  evaded  than  carried  out  by  the 
foundry  employes.  After  the  pipes  are  coated  and  upon  the  drying 
skid,  no  ordinary  inspection  can  determine  the  character  of  the  coat- 
ing other  than  its  appearance  to  the  eye  or  .touch. 

Testing  pipe  coatings  is  usually  by  the  hammer  to  see  whether 
the  coating  is  so  hard  and  brittle  as  to  chip  off  in  handling.  The  acid 
test  determines  the  porosity  of  the  coating  by  attacking  the  metal 
through  the  pores  of  the  dip.  A  solution  of  one  part  muriatic  acid  and 
two  parts  water  will  affect  both  the  coating  and  the  covered  metal 
more  at  the  end  of  sixty  days  than  they  would  be  affected  by  ten 
years'  exposure  to  running  water.  In  nearly  all  cases  where  the 

*  Excerpts  from  a  paper  by  Desmond  Fitzgerald,  C.E.  Transactions  Ameri- 
can Society  Civil  Engineers,  Vol.  XXXV,  1896,  p.  241. 


WATER-PIPE  DIPS  AND  COATINGS.  133 

coating  has  been  dried  by  heat  or  baked,  the  metal  will  be  corroded 
^Q  inch  or  more,  the  coating  undermined  and  peeled  off. 

After  all,  in  this  age  of  specifications,  inspections,  scrimping,  and 
adulterations,  there  is  nothing  equal  to  an  honest  and  capable  con- 
tractor, either  for  furnishing  pipe,  coating,  inspecting,  or  laying  it. 
Get  such  a  one  if  possible  and  then  watch  him  closely. 

Generally,  the  time  that  the  pipes  are  left  in  the  hot  bath  does 
not  exceed  one  minute,  and  is  more  often  only  one-half  a  minute.  It 
is  impossible  to  properly  coat  a  pipe  in  one-half  a  minute,  as  the  air 
carried  into  the  thick  turgid  bath  by  the  pipe  will  not  escape  in  that 
time,  and  the  top  part  of  the  inside  of  the  pipe  and  the  lower  part  of 
the  outside  of  the  pipe  are  uncertainly  coated  for  this  reason.  The 
pipes  are  seldom  turned  over  while  in  the  bath,  or  outside  while  on 
the  skids  in  the  process  of  scraping  and  brushing  off  the  surplus  dip. 

On  pipes  that  are  left  in  the  bath  for  five  minutes  the  coatings 
are  markedly  superior  to  those  exposed  for  shorter  periods.  This  is 
the  case  whatever  the  nature  of  the  coating,  and  is  one  reason  why 
the  Angus  Smith  and.  other  older-day  coatings  gave  such  superior 
results  to  those  coated  by  modern  methods.  They  never  had  less 
than  five  minutes  in  the  bath,  and  were  often  left  for  fifteen  or  even 
more  in  case  of  large  pipes  one  inch  or  more  in  thickness.  Modern 
pipe-foundry  management  allows  no  such  exposures. 

A  coal-gas  tar  paint  that  has  given  very  good  results  in  the  coating 
of  gas-holder  tanks  and  other  situations  where  the  metal  is  exposed  to 
ammonia  and  sulphurous  acids  in  solution  and  to  alternate  melting 
and  drying  under  a  great  range  of  temperature,  is  made  as  follows: 
Coal-gas  tar  is  well  boiled  to  evaporate  the  water  and  light  hydro- 
carbon elements  and  then  20  to  25  per  cent  of  caustic  quicklime  is 
sifted  and  well  stirred  in  to  neutralize  the  acid  elements  in  the  tar. 
This  is  to  be  kept  hot  for  a  few  hours  and  then  an  equal  quantity 
of  good  Portland  or  hydraulic  cement  is  sifted  and  stirred  in  thor- 
oughly. The  mixture  is  applied  hot  to  the  clean  dry  iron,  and  can 
be  repeated  soon  as  cool  or  dry  if  the  exposure  conditions  are  to  be 
very  severe.  In  the  latter  case,  a  little  more  cement  should  be  added, 
so  that  the  caustic  lime  and  cement  mixture  will  contain  50  per  cent 
of  each.  The  pigments  thicken  the  coal-tar  and  prevent  it  from  run- 
ning under  sun  temperatures  and  give  a  bond  to  the  brush  coating  of 
neat  Portland  cement  that  should  be  applied  to  the  coal-tar  coat  as 
soon  as  either  the  first  or  second  coat  of  the  mixture  is  dry.  This 
coating  can  be  repeatedly  applied  with  advantage.  It  is  impervious 


134 


PIPE-DIPPING  TANK. 


Derrick 
Hoist 


•  Asphalt 


to  gases   and  water  and  has  no  tendency  to  run  at  temperatures 
under  130°  to  140°  F. 

Mr.  Born,  in  "  Comptes  Rendes,"  in  1837,  called  attention  to  the 
fact  that  iron  cast  in  charcoal-coated  or  chilled-iron  moulds  was  less 
susceptible  to  corrosion  than  greensand  castings. 

The  city  of  Perth,  Scotland,  where  very  pure  water  is  obtained 
from  the  Tay,  had  their  water-pipes  coated  with  a  solution  of  india- 
rubber.  After  25  years  of  use  every  pipe  under  5  inches  in  diameter 
had  been  completely  closed  by  corrosion.  In 
many  cases  where  the  ordinary  coal-tar  dip 
had  been  used  on  the  water-pipes  it  scaled 
off  in  strips  and  was  discharged  at  the  house 
service-taps. 

A  pipe-dipping  tank  being  required  for 
some  steel  riveted  pipes,  16  to  30  inches  in 
diameter  and  28  feet  long,  was  extemporized 
from  old  material  in  the  contractor's  yard, 
and  is  shown  by  the  following  Fig.  21.* 

An  old  boiler-shell  3  feet  or  more  in  diameter 
and  26  feet  long  was  fitted  with  a  slightly 
dished  wrought-iron  flange  2  feet  or  more  in 
width  all  around,  riveted  to  the  top  end  of 
the  shell.  This  served  as  a  working  platform, 
also  to  catch  and  return  the  drip.  The  other 
end  or  lower  one  of  the  shell  was  riveted  and 
caulked  to  a  cast-iron  plate-head  which  car- 
ried on  its  inside  face  a  concentric  flange  in 
the  centre,  to  which  was  riveted  steam-tight 
a  wrought-iron  pipe  nearly  as  long  as  the 
outer  boiler-shell.  This  inside  pipe  was  closed 
steam-tight  by  a  conical  head  that  also  served 
as  guide  for  the  pipe  when  it  entered  the  bath 
of  pipe  dip.  The  bottom  flange  was  tapped 
for  steam-  and  drain-pipe  connections,  which 
were  fitted  with  the  usual  gates,  worked  from 


Level 


/^';;v/UD.ripv/;,,  ,/:,, 

F!Gt  21. — A  pipe-dipping  the  surface  of  the  ground,  in  or  on  which  the 
tank-  tank   was   erected.     The   annular  space   be- 

tween the  centre  pipe  and  shell  was  filled  with  the  coal-tar  or  other 
pipe  dip  to  be  applied  to  the  pipe,  which  was  kept  hot  by  the  steam 

*  Engineering  Record,  Vol.  XXXV,  May  8,  1897,  p.  489. 


WATER-PIPE  DIPS  AND  COATINGS. 


135 


in  the  centre  pipe.  The  immersion  and  withdrawal  of  the  pipe  to  be 
coated  kept  the  bath  mixture  well  stirred  up  and  ensured  a  nearly 
uniform  quality  of  its  ingredients.  It  is  obvious  that  this  compara- 
tively inexpensive  device  is  adaptable  for  many  occasions  that  would 
not  warrant  a  more  expensive  plant. 

A  larger  shell  could  be  fitted  with  a  number  of  the  conical- 
headed  pipes  with  their  separate  steam-  and  drain-pipe  connections 
and  be  available  for  dipping  a  number  of  pipes  at  the  same  time,  and 
would  certainly  ensure  a  more  reliable  coating  than  where  the  pipes 
are  immersed  in  a  long  horizontal  tank. 

APPROXIMATE  RELATIVE  COST  OF  VARIOUS  PIPE-DIPS  AND  COATINGS.* 


Coating. 

Approximate 
Amount  Re- 
quired to 
Coat  One  48- 
inch  Pipe,  12 
Ft.  Long. 

Approximate  Prices. 

Cost  of 
Material  for 
One  48-inch 
Pipe.     Ap- 
proximately 
325  Sq.  Ft. 
of  Surface. 

Crude  tar  

3f  gals. 

$3.00  per  bbl.  (52  gals.) 

$0.22  a 

Pitch. 

5      " 

5  00    "      "      "       " 

0  50 

Pitch  and  linseed-oil  

70 

P.  &  B.  dip  

20  Ibs 

45  00  per  ton 

45 

Mineral  dip.  .  . 

20     " 

75  00    "     " 

75 

P.  &  B.  universal  paint  
P.  &  B.  ruberine  .  . 

14  gals. 
U    " 

1.00  per  gal. 
1  00    "      " 

1.506 
1  506 

Tar  varnish 

U    " 

0  10    "     " 

15  b 

Dutch  varnish 

U    " 

0  25    "     " 

40  b 

Sabin's  baked  japan 

U    " 

1  75    "     " 

2  60  c 

a.  About  30  per  cent  of  this  was  lost  by  evaporation. 

b.  Estimated  cost  of  this  coating  as  applied  with  a  brush.     The  wastage 
would  be  excessive  as  a  dip,  but  the  dip  is  the  only  practical  way  for  its  use  on  a 
large  scale,  hence  the  figures  are  not  strictly  correct. 

c.  This  coating  requires  a  comparatively  expensive  plant  and  considerable 
skilled  labor,  which  would  largely  increase  the  total  cost. 


*  "  The  Manufacture  and  Inspection  of  Cast-iron  Pipes."     Thos.  H.  Wiggins, 
C.E.,  Boston.     Civil  Engineers'  Association  Journal,  1899. 


CHAPTER  XIII. 

GRAPHITE   AND    GRAPHITE    PAINTS. 

CARBON  assumes  in  nature  three  allot ropic  forms,  viz. :  Diamond, 
graphite,  and  amorphous  carbon.  Graphite  itself  assumes  different 
forms,  some  of  which  are  amorphous  and  others  strictly  crystalline  in 
character. 

If  the  three  allotropic  forms  of  carbon  had  each  a  characteristic 
name,  no  confusion  would  be  liable  to  arise  in  speaking  of  them.  We 
speak  of  the  diamond  and  of  graphite,  and  each  is  clearly  defined. 

In  speaking  of  the  third  form  we  are  limited  to  amorphous  carbon. 
This  form  is  found  in  certain  stages  which  are  not  strictly  amorphous 
or  granular  in  character.  Coke,  for  instance,  is  one  form;  the  others 
are  the  mineral  graphite-carbon  or  graphite,  termed  foliated  (flake), 
amorphous  (granular),  etc.  Graphite  is  found  in  many  parts  of  the 
world  and  is  of  various  degrees  of  purity,  ranging  from  60  to  over  90 
per  cent  of  graphitic  carbon  in  the  foliated  form  and  20  to  60  per  cent 
in  the  other  forms. 

The  foliated  is  a  designation  for  the  thicker  flakes  in  the  Ceylon 
and  like  varieties,  while  flake  is  used  to  designate  the  thin  flakes  of 
the  purest  brands,  similar  to  the  Ticonderoga  mine  product. 

The  German  (Bavarian),  Siberian,  Mexican,  and  some  American 
varieties  are  amorphous  and  vary  greatly  in  the  amount  of  carbon  in 
their  composition,  as  will  be  seen  from  the  following  analyses: 

The  purest  brands  (Ticonderoga  mine)  have  a  specific  gravity  of 
1.21  to  1.4.  The  amorphous  varieties  range  from  1.80  to  2.25  to  2.79. 
When  pure  it  is  perfectly  opaque,  iron-black  or  steel-gray  in  color, 
with  a  metallic  lustre.  Its  hardness  varies  from  1  to  2,  and  it  con- 
ducts electricity  nearly  as  well  as  the  metals. 

Pure  graphite  or  minerals  high  in  graphite-carbon  grind  and  feel 
greasy,  and  are  repellent  to  moisture  and  oil.  Flake-graphite  above 
80  per  cent  in  purity,  by  long  trituration  with  water,  can  be  reduced 
to  a  fine  lamina  or  pigment. 

Anthracite  coal  is  an  intermediary  carbon  between  graphite  and 

136 


GRAPHITE  AND  GRAPHITIC  CARBON.  137 

bituminous  coal.  It  is  blacker  than  graphite,  hardness  2  to  2.1  as 
against  1  to  2  for  graphite  when  it  contains  95  to  99  per  cent  of  carbon. 

The  Ceylon,  Cumberland,  Indian,  and  American  flake  varieties 
are  the  purest  in  carbon,  and  are  used  for  pencils,  crucibles,  lubricants, 
stove-polish,  foundry  facings,  etc.,  and  to  tone  up  the  poorer  varieties 
for  many  purposes. 

Foliated  graphites,  though  used  for  pigments,  are  not  as  satisfac- 
tory (for  reasons  given  hereafter)  as  the  amorphous  variety,  that,  less 
rich  in  carbon,  contains  other  mineral  substances,  non-corrosive,  non- 
absorbent  of  atmospheric  moisture  and  gases,  either  as  individual  sub- 
stances or  collectively  as  a  natural  mineral  compound.  That  this 
feature  may  be  duly  considered  when  a  graphite  pigment  is  to  be 
selected  for  a  ferric  structure  the  following  analyses  of  amorphous 
graphite  from  a  number  of  widely  separated  mines  are  given: 

ANALYSES  OF  AMORPHOUS  GRAPHITE. 

Siberian  and  German  Mines. 

Per  Cent.  Per  Cent. 

Graphitic  carbon 33.20  to  36.06  28.39  to  33.48 

Silica  as  SiO2 43.20  "  37.70  46.97  "  37.54 

Iron  soluble  as  Fe203 »    3M  «     4.02  4.22"     4.25 

"    insoluble  \ 

Alumina  as  A12O4   15.42  "  17.80  16.90  "  12.35 

CalciumasCaO i 

Magnesia  as  MgO.      ) 

Carbon  dioxide,  water  combined,  so- 
dium compounds,  iron  pyrites,  vola- 
tile matter  and  loss 4.09"  3.22  2.53"  1.36 

Specific  gravities,  2.25  to  2.79.  Color,  gray  or  drab.  Hardness, 
1.5  to  1.8.  Fracture,  granular. 

Graphite  from  the  Wisconsin  mines  analyzes,  viz.: 

Graphitic  carbon 72.00  to  74.00  per  cent 

Iron  oxide 7.10  "  14.00    "      " 

Silica 10.00  "  12.00    "      " 

Alumina 8 .00    '  traces 

Water  and  undetermined 2.90"       " 

The  Mexican  graphites  are  amorphous  in  character,  are  high  in 
carbon,  and  have  had  but  a  limited  use  for  pigments.  When  contain- 
ing about  80  per  cent  of  carbon  they  are  better  suited  for  lubricants 
or  foundry  facings. 

The  amorphous  brands  of  graphite  require  no  calcination  other 
than  necessary  to  dispel  the  water,  natural  to  all  minerals,  prepara- 


138  GRAPHITE  AND  GRAPHITIC  CARBON. 

tory  to  any  pulverizing  operations.  They  grind  fine  and  granular, 
and  in  an  approximately  cubical  form,  are  not  repellent  to  the  oil 
or  vehicle,  and  are  nearly  as  unoxidizable  from  moisture,  atmospheric 
influences,  combustion,  and  other  gases  as  pure  carbon.  They  are 
of  an  agreeable  color  and  good  covering  power,  and  they  work  well  in 
combination  with  other  pigments ;  flow,  hold,  or  carry  well  in  the  oil, 
and  are  as  easily  brushed  out  to  cover  as  much  surface  as  any  good 
paint.  They  are  not  repellent  to  the  oil,  do  not  separate  from  it, 
nor  set  in  the  paint  pot  or  barrel  on  long  storage,  either  as  a  paste  or 
paint.  They  are  wholly  self-supporting  as  pigments,  contain  no 
elemental  substances  that  tend  to  reduce  them  to  a  lower  plane  by 
oxidation  or  slacking  in  the  presence  of  moisture  and  gases.  They 
require  no  body  stuffing,  either  to  bond  them,  or  to  keep  them  quiet, 
or  from  curdling  or  crawling  during  or  after  application,  and  they 
contain  neither  acids  nor  sulphur. 

They  are  entirely  different  in  character  and  composition  from 
the  so-called  silica  graphites  of  commerce,  many  of  which  resemble 
carbonaceous  schists  or  impure  soapstone,  or  are  compounded  from 
flake-graphite  and  mineral  substances  of  dissimilar  character,  such 
as  barytes,  silica,  furnace  slag,  etc.  These  several  substances,  even 
if  they  are  non-corrosive,  or  electrically  or  chemically  passive  of  them- 
selves or  collectively,  when  assembled  in  a  paint  cannot  be  as  reliable 
as  are  the  same  substances  incorporated  together  by  the  processes 
of  nature,  each  and  every  particle  of  which  is  of  the  same  physical 
and  chemical  composition  and  equally  affected  by  the  vehicle, 
atmosphere,  or  other  conditions  that  affect  a  paint. 

They  have  not  the  merit  of  being  synthetical  compounds.  No 
human  care  in  the  mechanical  processes  of  grinding  and  mixing  them, 
as  a  compound  pigment  or  paint,  can  arrange  them  in  sequence  or 
in  other  than  a  haphazard  manner. 

Silica  graphite  paint  is  of  a  dark,  lifeless  brown ;  not  objectionable 
on  the  enclosed  ironwork  of  a  building,  but  decidedly  so  for  more 
prominent  positions.  Hence  it  is  toned  up  by  red  lead  or  other  basic 
pigments  of  agreeable  color,  but  at  an  increased  cost  and  a  contributed 
element  of  danger  in  the  disintegrating  of  the  paint  whenever  hydric- 
sulphide  fumes  reach  the  red  lead  in  the  coating. 

Iron  oxide  is  also  used  for  toning  effects,  but  the  natural  red  hema- 
tite oxides  are  not  strong  enough  in  color  to  materially  modify  the 
dark  brown  of  the  graphite,  silica,  and  barytes  compound,  unless  exces- 
sive quantities  are  used,  which  bring  into  the  coating  all  of  the  uncer- 


GRAPHITE  AND  GRAPHITE  PAINTS.  139 

tain  elements  of  that  class  of  pigments  that  thus  far  have  proven  to 
be  the  most  unreliable  of  all  ferric  coatings.  The  danger  is  greater 
if  the  brighter  red  copperas  oxides  are  used.  Their  strong  sulphur 
element  sets  into  action  an  antagonism  between  every  element  in  the 
coating  and  delays  the  drying  of  the  paint,  making  necessary  exces- 
sive amounts  of  strong  driers  to  counteract  even  a  small  percentage  of  it. 

Graphite  paints  are  noted  for  being  slow  driers  and  require  a  lib- 
eral use  of  driers  to  get  a  firm  coating.  This  is  more  apparent  with 
flake-graphite;  its  flocculent  form  and  oily  nature  prevent  the  vehicle 
from  bonding  it.  There  is  a  movement  in  the  paint  during  the  whole 
process  and  period  of  drying  that  even  the  sharper  and  more  angular 
form  of  the  silica  or  barytes  added  cannot  wholly  overcome.  Further- 
more, these  substances  bring  their  own  peculiarities  into  the  coating 
and  forcibly  demonstrate  the  unreliable  character  of  all  compound 
paints.  The  greater  the  number  of  substances  in  a  paint  the  less 
dependence  can  be  placed  upon  them  to  work  together  for  a  durable 
coating.  An  acid  and  an  alkali  will  chemically  form  an  innoxious 
whole,  but  this  or  similar  action  is  dangerous  in  a  drying  paint  and 
generally  proves  detrimental  to  the  coating  or  covered  surface. 

High-carbon  graphite  is  so  easily  adulterated  with  soapstone  that 
if  a  pound  of  it  be  ground  with  three  pounds  of  soapstone  (specific 
gravity  2.7),  neither  the  eye  nor  touch  can  detect  the  adulteration; 
only  analysis  will  show  it. 

Graphite  is  one  of  the  lightest  pigments.  Its  specific  gravity 
ranges  from  1.21  to  1.4  to  2.38,  while  zinc  oxide  is  5.42,  asphaltum 
1.4  to  1.8,  barytes  4.5  to  4.7,  silica  1.9  to  2.8,  gypsum  2.15  to  2.35,  iron 
oxide  4.7  to  5.4,  whiting  2.2  to  2.8,  red  lead  9.07,  white  lead  6.43. 

The  natural  drying  of  a  linseed  or  varnish  coating  is  in  the  form 
of  a  closely  woven  web  of  a  fine  fabric.  This  shows  plainly  on  a  freshly 
dried  or  drying  surface,  and  explains  the  reason  why  two  or  more 
coats  are  necessary  to  give  a  smooth  foundation  for  the  last  or  polish- 
ing coat.  Each  subsequent  coat  fills  the  interstices  of  that  under- 
neath it,  each  coat  repairing  the  other's  deficiencies,  as  many  folds  of 
a  fine  muslin  will  in  the  aggregate  make  an  adequate  covering  from 
heat  or  light. 

Now,  it  is  the  function  of  a  pigment  to  fill  these  cellular  forma- 
tions in  the  drying  vehicle,  or  rather,  while  being  applied  with  a  brush, 
for  the  atoms  of  the  pigment,  mechanically  arranged  in  brushing  out 
the  paint,  to  lie  side  by  side,  all  embedded  in  the  vehicle,  which  in 
drying  naturally  takes  the  lines  of  least  resistance,  i.e.,  between  the 


140  DRYING   OF  GRAPHITE  PAINTS 

pigment  atoms,  and,  as  it  were,  each  atom  lies  in  an  approximately 
square  hole,  the  most  favorable  condition  for  the  bond  between  the 
pigment  and  the  vehicle. 

If  the  pigment  atom  be  splintered  like  a  sliver  of  glass,  or  of  only 
length  and  breadth  like  a  flake,  then  the  natural  cellular  formations 
in  the  drying  vehicle  cannot  be  realized.  Such  shaped  pigments  are 
arranged  with  the  sharpest  angles  and  edges  upright  to  the  drying 
surface,  and  are  not  well  covered  in  or  embedded  in  the  oil,  hence 
dry  with  a  rough  surface  that  will  hold  moisture  and  dust  and  quickly 
decompose  and  disintegrate  them  from  their  bed,  when  more  moisture, 
cinders,  and  dust  take  their  place  and  the  cycle  of  action  is  repeated. 

The  rough  character  of  all  paint  coatings  containing  silica,  barytes, 
furnace  slag,  etc.,  is  distinctly  apparent  to  the  touch.  A  round  marble 
does  not  bed  itself  in  a  cement  as  well  as  the  cubical  block  from  which 
it  is  made,  neither  does  a  beach-worn  sand  or  a  quicksand  atom, 
with. the  best  of  cement,  make  a  good  mortar  for  the  same  reason. 
The  splinters,  flakes,  and  round  atoms  are  more  easily  removed  from 
their  beds  than  a  square  atom. 

Both  the  amorphous  and  flake  graphite  pigments  (not  associated 
with  foreign  substances  as  adulterants)  being  electro-negative,  are 
less  affected  by  catalytic  or  electrolytic  action  caused  by  the  juxta- 
position of  electro-positive  substances  in  the  coating  or  surface 
covered,  or  by  hydro-sulphide  gases,  than  any  class  of  pigments, 
lampblack  alone  excepted.  This  is  a  valuable  feature  in  any  paint, 
whether  applied  to  iron  or  wooden  bodies,  and  in  the  future  will  insure 
a  more  extended  use  of  graphite  paints  instead  of  the  iron  oxides, 
and  compounded  or  patent  paints,  to  the  careless  use  of  which  most 
of  the  corrosion  in  progress  upon  important  ferric  structures  is  di- 
rectly traceable. 

As  a  general  rule  graphite  minerals  that  contain  about  40  per 
cent  of  graphitic  carbon  have  proven  to  be  better  for  pigments  than 
those  richer  in  carbon,  for  the  reasons  given  before,  the  principal 
one  being  that  they  are  less  repellent  to  the  oil  and  bond  better  to  it, 
and  do  not  appear  to  be  affected  by  combustion  gases. 

Amorphous  graphite  coating  applied  to  boiler  tubes  exposed  to 
internal  firing  and  the  action  of  hot  water  under  pressure  of  eighty 
or  more  pounds  per  square  inch  for  two  years  was  uninjured  and 
fresh  as  when  it  was  first  applied. 

Fig.  22  shows  a  boiler-tube  thus  exposed.  The  tubes  had  been 
in  the  boiler  for  a  number  of  years,  when  they  were  removed  and 


DRYING  OF  GRAPHITE  PAINTS.  141 

cleaned  from  the  hard  silicious  scale  that  covered  them.  When  they 
were  replaced,  each  alternate  tube  was  coated  with  Lake  Superior 
graphite  paint,  the  others  being  uncoated.  At  the  end  of  over  two 
years  a  number  of  the  tubes  were  removed  and  their  condition  as- 
certained. The  unpainted  ones  were  again  covered  with  the  hard, 
flinty  scale,  that  required  the  use  of  a  boiler-scraper  to  remove.  The 
painted  tubes  were  covered  with  a  light  flocculent  coating  of  the  scale, 
that  could  be  brushed  off  with  the  ringers,  showing  the  bright,  clean 


FIG.  22.— Boiler-tube. 

paint  beneath  it.  The  tubes  were  pitted  with  rust  in  spots  and 
streaks  when  they  were  first  removed  to  be  cleaned.  These  show 
in  the  photograph,  but  the  corrosion  was  stopped  by  the  paint.  The 
light-colored  scale-deposit  was  left  on  part  of  the  tube,  and  shows 
on  the  sides  of  the  figure. 

Pieces  of  iron  coated  with  graphite  paint  and  dipped  in  muriatic, 
sulphuric,  and  nitric  acids,  and  allowed  to  dry  with  the  acid  on  them 
showed  at  the  end  of  nineteen  days  no  injury  to  the  coatings.  Other 
samples  immersed  in  alkaline  and  other  chemical  solutions,  also  in 
coal-oil  for  a  number  of  weeks,  and  strong  brine  for  months,  showed  but 
little  injury.  Other  tests  of  endurance  of  all  brands  of  graphite  paints 


142  ELECTRIC-FURNACE  GRAPHITE. 

showed  a  marked  superiority  over  other  basic  pigments,  whether 
prepared  for  a  test  or  compared  with  the  commercial  brands  of  other 
paints. 

While  tests  of  paints  are  not  regarded  by  many  engineers  as 
indicative  of  their  value  to  resist  the  ordinary  influences  upon  a  coat- 
ing exposed  to  weather,  they  do  show  that  a  coating  that  can  withstand 
the  above  severe  tests  is  certain  to  give  more  satisfactory  results 
in  its  general  use  than  the  many  commercial  paints  whose  low  price 
and  not  their  protective  qualities  is  their  principal  recommendation. 
They  also  show  that  if  the  conditions  to  which  a  coating  is  to  be 
subjected  are  known,  it  can  generally  be  furnished  to  successfully 
meet  them. 

Other  tests  of  graphite  paints  in  competition  with  other  commer- 
cial paints  are  given  in  the  following  chapters  on  paint  tests.  For 
a  roofing  paint  the  graphites  high  in  carbon,  of  themselves,  or  mixed 
as  silica-graphite  compound  paints,  are  of  marked  excellence.  They 
do  not  harden  as  rigidly  as  the  iron  oxides  used  for  roofing  purposes. 
They  endure  long  exposure  to  the  sun,  hence  are  less  liable  to  crack 
or  flake  off,  and  they  follow  without  injury  the  expansion  changes 
in  the  metal  they  cover.  Their  darker  color  and  higher  cost  com- 
pared with  iron-oxide  paints  used  for  roof  coatings  are  more  than  offset 
by  their  better  protective  qualities  and  longer  life. 

Electric-furnace  Graphite. 

However  engineers  may  differ  about  the  respective  merits  of  a 
low  or  medium  grade  of  amorphous-graphite  mineral  for  a  straight 
paint  compared  with  a  flake-graphite  and  silica  compound,  their 
attention  is  liable  to  be  attracted  in  the  future  to  a  new  product 
that  has  entered  the  field  for  a  pigment,  under  the  name  of 

"  Acheson  Graphite." 

This  substance  is  an  amorphous-graphite  pigment  of  high-carbon 
content,  whose  physical  character  seems  to  be  materially  different  from 
the  high-carbon  mineral  graphites  heretofore  used  for  paints.  Although 
amorphous  or  granular  in  character,  as  compared  with  the  other 
forms  of  graphite,  such  as  the  flake-graphites,  it  is  nevertheless  dis- 
tinctly a  graphite  product,  and  contains  absolutely  no  trace  of  amor- 
phous carbon,  the  name  usually  applied  to  such  forms  of  carbon  a& 
lampblack,  coke,  coal,  etc.  Graphite  hi  any  form  is  much  more  inert 
chemically  than  these  amorphous  carbons,  but  Acheson  graphite  is- 


ACHESON    GRAPHITE.  143 

even  more  inert  than  any  of  the  natural  graphites.  Its  specific  grav- 
ity is  2.25.  It  is  ground  dry  and  air-floated  to  an  exceedingly  fine 
state  of  subdivision  and  of  great  uniformity  in  size  of  the  individual 
particles. 

Its  amorphous  character  renders  it  far  less  repellent  to  the  oil 
than  the  natural  graphites  containing  approximately  the  same  per- 
centage of  carbon.  This  quality  causes  it  to  remain  in  place  in  the 
oil,  and  it  is  not  as  easily  moved  out  of  position  by  the  drying  action 
of  the  vehicle,  as  is  the  case  with  a  high-carbon  flake-graphite. 

Acheson  graphite  used  with  a  boiled-oil  vehicle  will  set  in  the 
coating  without  the  aid  of  any  inert  substance  to  hold  it  in  place 
while  drying.  Used  with  raw  oil,  it  requires  a  drier  to  secure  the 
initial  set  of  the  paint,  particularly  if  the  coating  is  to  be  an  ex- 
ternal one  exposed  to  the  vicissitudes  of  weather. 

Its  manufacture  is  entirely  unlike  that  of  any  other  pigment,  and 
is  shown  by  Fig.  23,  illustrating  the  style  of  the  special  electric  furnace 
used  to  produce  it. 

In  manufacturing  graphite  in  this  way,  anthracite  coal  is  heated 
several  hours  in  the  electric  furnace  by  means  of  a  powerful  electric 
current,  approximating  1000  horse-power  of  energy.  The  tempera- 
ture of  the  mass  of  coal  is  raised  to  a  point  where  the  carbon  is  con- 
verted into  carbides  of  the  various  constituents  of  the  ash,  which 
in  anthracite  coal  are  very  evenly  distributed.  The  temperature  is 
then  carried  to  the  point  where  the  carbides  are  decomposed,  and 
the  principal  constituents  of  the  original  ash,  silicon,  iron,  sulphur, 
aluminum,  etc.,  are  driven  off  as  vapors. 

The  residue  removed  from  the  furnace  is  carbon  in  the  form 
of  graphite,  perfectly  free  from  any  trace  of  the  amorphous  carbon 
or  coal  from  which  it  was  produced.  Its  method  of  manufacture  is 
probably  a  duplication,  upon  a  small  scale,  of  the  process  by  which 
the  natural  graphites  were  formed  in  the  earth.  The  purity  of  the 
product  depends  upon  the  temperature  to  which  it  has  been  raised; 
for  commercial  purposes,  it  contains  about  90  per  cent  of  carbon.  The 
10  per  cent  of  ash  still  remaining  in  the  carbon  is  practically  as  inert 
as  the  graphite  itself,  and  intimately  associated  with  it.  The  furnace 
product  is  broken  up,  and  the  grades  suitable  for  various  purposes 
separated.  The  grade  used  for  a  pigment  is  pulverized  to  an  im- 
palpable powder,  and  air-floated  for  collection.  In  the  latter  stage 
it  contrasts  strongly  with  the  poorly  ground  and  coarse  particles  of 
many  of  the  mineral-graphite  pigments,  and  like  a  properly  made 


144  ACHESON.  GRAPHITE. 

lampblack  or  a  sublimed-lead  product,  it  has  the  physical  character 
for  an  ideal  paint. 

Unfortunately,  there  is  no  standard  for  a  graphite  paint  as  there 
is  for  a  pure-white  or  red-lead  paint.  The  consequence  is,  that  where 
graphite  paint  is  specified  by  the  engineer,  he  is  to  an  extent  working 
in  the  dark,  and  does  not  feel  at  all  sure  but  that  the  coating  will  be 
spread  from  some  one  or  other  of  the  many  abominations  under  the 
guise  of  "mixed  paint/'  that  has  not  an  atom  of  graphite  of  any 
kind  in  it.  Reputation  of  the  manufacturer  or  dealer  in  graphite 
pigments  or  paints  is  quite  as  essential  as  in  the  case  of  the  lead  and 
zinc  products.  Adulterations  in  a  graphite-mixed  paint  are  more 
easily  concealed  from  the  eye  than  in  those  having  a  lead  or  zinc 
base,  and  are  equally,  if  not  more,  annoying  to  the  engineer. 


CHAPTER  XIV. 

BESSEMER      PAINT. 

A  SPECIAL  pigment,  claimed  to  be  of  the  inert  class,  has  lately 
come  into  use  to  replace  oxide  of  iron  as  a  straight  paint  for  ferric 
structures.  During  the  short  period  it  has  been  upon  the  market,  its 
use  has  been  attended  with  many  favorable  results.  It  is  a  German 
development,  and  is  reported  to  be  the  pulverized  slag  from  Besse- 
mer basic  process  steel  furnaces.  It  is  claimed  to  be  free  from  the 
sulphur  and  phosphoric  acid  elements  that  are  usually  present  in 
iron-oxide  pigments. 

It  is  prepared  as  a  mixed  paint  ready  for  use.  The  finely  pulver- 
ized furnace  slag  is  ground  in  linseed-oil  containing  a  small  amount  of 
one  of  the  copal  resins  that  makes  the  paint  coating  very  elastic 
even  after  long  exposure  to  the  sun. 

It  is  claimed  to  spread  easily,  covering  1000  square  feet  per  gallon; 
but  to  do  this  the  use  of  short  bristle  brushes  is  recommended,  the 
effect  of  which  is  to  rub  out  the  coating  very  thin.  But  however 
closely  the  paint  may  thus  be  forced  into  contact  with  the  surface 
being  covered,  it  cannot  be  as  well  protected  as  where  the  paint  is 
spread  by  long  bristle  brushes,  and  a  sufficient  amount  of  painters' 
labor  and  time  is  given  to  spread  the  coating.  The  pigment  is  not  so 
deeply  embedded  in  the  vehicle,  nor  so  well  protected  or  bonded  to 
the  coated  surface  as  it  is  when  spread  over  a  smaller  area. 

Bessemer  paint  in  its  natural  color  is  a  very  dark  gray,  though  it 
can  be  made  a  lighter  shade  by  the  addition  of  other  substances  (not 
of  its  own  nature)  to  tint  it.  In  this  case  the  coating  will  be  no  more 
durable  than  the  life  of  the  most  perishable  pigment  in  the  paint,  as 
is  the  case  with  all  compound  paints. 

Bessemer  paint  weighs  12£  pounds  and  costs  $1.50  per  gallon, 
and  is  claimed  to  dry  in  24  hours  without  the  use  of  added  driers,  which 
seems  to  indicate  that  the  vehicle  carries  an  energetic  drier  not 
natural  to  a  linseed-oil  and  copal  vehicle,  as  the  pigment  has  no  dry- 
ing quality  different  from  that  of  any  iron-oxide  pigment.  The 

145 


146  BESSEMER  PAINT. 

quick  drying  of  the  coating  is  also  aided  by  atmospheric  exposure,  but 
when  the  slags  are  pulverized,  these  features  will  not  protect  any 
associated  pigment  or  substance  from  the  action  of  the  atmosphere. 
All  slag  pigments  are  electro-negative  to  the  metallic  base  pigments, 
and  to  all  of  the  metals  that  constitute  a  part  of  their  composition, 
also  to  the  metallic  surface  that  is  coated  with  them. 

Insulating  qualities  are  claimed  for  Bessemer  paint;  but  other 
paints  free  from  metallic  oxides  also  have  this  quality.  The  insulat- 
ing qualities  of  any  paint  are  due  to  the  vehicle  more  than  to  the  pig- 
ment, with  the  single  exception  of  india-rubber.  In  any  case,  a  paint 
coating  cannot  resist  electrical  currents  of  high  potential;  to  mod- 
erate or  low  potential  the  insulation  would  be  more  or  less  resistant 
according  to  the  amount  of  resinous  matter  in  the  vehicle.  In 
this  respect  Bessemer  paint,  containing  as  it  does  a  small  amount 
of  fossil  resin,  would  be  better  than  a  paint  containing  none. 

Common  resin  or  resin  oil  should  not  be  substituted  for  copal; 
they  are  not  desirable  elements  in  a  paint,  as  they  dry  hard  and 
crack  the  coating  or  cause  it  to  crumble  and  rub  off  after  a  short 
exposure  in  the  open  air  or  sunlight,  and  they  promote  corrosion.  (See 
Paint  Tests,  Chapter  XXIX.) 

Pulverized  mineral  wool  has  been  proposed  for  a  pigment.  It  is 
a  furnace  slag  riven  when  in  a  molten  state  by  a  current  of  steam. 
But  merely  pulverizing  it  imparts  no  protective  value  to  it  for  a 
pigment.  It  is  acid  in  reaction,  electro-negative  in  character,  and 
when  used  for  covering  steam-pipes  or  other  ferric  bodies,  on  becoming 
damp  is  a  virulent  agent  for  promoting  corrosion.  A  sample  of  min- 
eral wool  analyzed  by  Prof.  Egleston,  of  Columbia  University,  gave 
the  following  result: 

Insoluble 
in  Water. 


19.70 
24.95 
0.64 
7.84 
38.97 

2.32 
99.49  5.07  94.42 


Substances. 
Water  

Per  cent. 
1  08 

Soluble 
in  Water. 
1   08 

Potash 

0  19 

0   19 

Soda  

1  75 

1  75 

Magnesia  

19  82 

0  12 

Lime.  ...                      .    . 

26  56 

1  61 

Sesquioxide  of  iron  

0  64 

7  84 

Silica  

38  97 

Sulphur  (mostly  as  a  sulphide, 
probably,  of  calcium)  

2.64 

0.32 

BESSEMER   PAINT.  147 

The  composition  of  this  slag  is  not  much  different  from  the  preceding 
analysis  of  blast-furnace  slag,  and  with  it  may  be  taken  as  representa- 
tive of  this  class  of  substances. 

No  analysis  of  the  Bessemer  pigment  is  given  by  the  manufacturers 
of  the  paint.  It  is,  however,  supposed  to  be  a  tetra-basic  phosphate 
of  lime,  containing  about  20  per  cent  of  phosphoric  acid  and  50  per 
cent  of  lime,  associated  with  other  mineral  and  metallic  substances 
in  Bessemer  iron  ores.  Some  of  these  substances  are  partially  con- 
sumed in  the  working  of  the  furnace,  and  the  balance  fluxed  off  as 
Bessemer  basic  slag. 

Bessemer  basic  process  steel  was  made  by  the  Pottstcwn  Iron 
Co.,  of  Pottstown,  Pa.,  for  a  few  years  previous  to  1893,  and  the  pul- 
verized slag  was  sold  for  a  fertilizer.  Since  1893  the  basic  process 
for  making  steel  has  been  suspended  in  America,  and  the  slag  is  now 
procured  from  Germany. 

ANALYSIS  OF  BESSEMER  CONVERTER  BASIC  SLAG. 

Phosphoric  acid 21 .37  per  cent. 

Lime 45.26    "      " 

Ironcxide 12.00"  -      J  Equal  to  8.40  per  cent  of 

1      metallic  iron. 

Silica 5.10    "  " 

Magnesia 5.90    "  " 

Alumina 4 .01    "  " 

Soda  and  potash 0 .80    "  " 

Manganese  oxide          5 . 56    "  " 

100.00    "      " 

An  analysis  of  blast-furnace  slags,  the  mean  of  2000  samples 
from  furnaces  working  on  gray  forge  pig  iron,  is  given  for  a  comparison 
with  the  Bessemer  converter  slag. 

Silica 43 . 07  per  cent. 

Lime 28.70    "      " 

Alumina 14.83    "      " 

J 

Peroxide  of  magnanese 1 . 37  "  " 

Magnesia 5.46  "  " 

Potash 1.84  "  " 

Calcium 1.01  "  " 

Sulphur, 0 .89  "  " 

100.00    "      " 
Specific  gravity  2.8  to  3.2.     Fracture  vitreous,  similar  to  broken 


Ironoxide 2.83"      «      ^  Equal  to   1 . 98  per  cent  of 

metallic  iron. 


148  BESSEMER  PAINT. 

earthenware.  Color  dark  gray,  tending  to  the  darker  or  brownish 
shades. 

Blast-furnace  slags  are  acid  in  reaction,  while  Bessemer  slag  is 
basic  or  neutral.  Both  are  pyrogenic  bodies  unaffected  by  heat  or 
sunlight,  and  neither  is  oxidized  by  the  atmosphere. 

A  German  chemist .*  gives  the  analysis  of  Bessemer  paint,  as  known 
to  the  trade  in  Germany,  as  follows:  "The  pigment  contains  baryta, 
alumina,  iron  oxide,  lime,  silica,  zinc  oxide,  sulphuric  acid,  carbon 
dioxide,  and  phosphoric  acid."  No  definite  percentages  of  these 
substances  are  given  in  the  analysis,  nor  any  mention  whether  they 
were  separate  constituents  of  the  paint  assembled  in  the  process 
of  grinding  and  mixing,  or  that  any  number  of  them  were  found  com- 
bined together  as  a  single  pigment.  "Graphite  or  other  carbon  is 
used  as  coloring  matter,  and  linseed  varnish  as  the  vehicle,  turpentine 
constituting  the  drier.  The  presumptive  constitution  is,  therefore, 
lithopone,  or  silicious  calamine  ore,  containing  baryta  and  chalk, 
together  with  graphite  or  other  form  of  carbon,  and  linseed  varnish 
(with  probably  turpentine  as  a  drier).  When  treated  with  hydro- 
chloric acid  it  disengages  sulphureted  hydrogen." 

There  are  many  formulae  for  compound  pigment  paints  in  this 
country,  each  of  some  declared  excellence  by  the  manufacturers  of 
them,  if  not  by  the  users;  but  it  is  difficult  to  select  one  that  for  the 
varied  composition  will  equal  this  German  product.  Whatever  may 
be  the  composition  of  the  American  brand  of  "Bessemer  paint/'  it 
appears,  from  the  above  description,  to  be  wholly  unlike  that  of  its 
German  namesake,  and  is  certainly  superior  to  it  for  a  ferric  paint. 

*  "Andes'  Iron  Corrosion." 


CHAPTER  XV. 

NATURAL-ROCK  HYDRAULIC  CEMENT. 

HYDRAULIC-CEMENT  coatings,  either  in  the  form  of  a  plaster  coat 
laid  on  by  a  trowel  or  as  a  wash  or  brush  coating,  have  not  been  much 
used  for  the  protection  of  ferric  structures  as  a  substitute  for  paints, 
though  its  use  as  a  protection  from  corrosion  of  iron  embedded  in 
masonry  is  common  and  its  value  for  this  purpose  under  certain  condi- 
tions is  recognized. 

Hydraulic  cement  made  from  the  ground  mineral  varies  greatly 
in  quality,  its  general  composition  after  calcination,  that  makes  it 
caustic  and  anhydrous,  being: 

Lime.  ......   50  to  80  per  cent  i 

Clay 25  "  40    "       "    >•  Specific  gravity,  1.5  to  1.6. 

Iron  oxide..     3  "  14    "      "    ) 

Silica,  sand,  magnesia,  sulphur,  and  many  metallic  oxides  are  also 
present  in  some  amounts  in  many  varieties  of  the  hydraulic  mineral, 
all  of  which  affect  the  quality  of  the  cement  unfavorably  when  it  is 
used  for  a  mortar,  and  are  more  objectionable  when  it  is  to  be  used 
for  a  coating  on  ferric  bodies. 

The  adulteration  of  mineral  hydraulic  cement  is  generally,  from  the 
same  class  of  minerals  of  inferior  quality,  with  free  sand,  silica,  and 
iron  ores  containing  sulphur  in  the  form  of  sulphides,  and  all  are  imper- 
fectly roasted  and  pulverized. 

Their  setting  quality  and  strength  are  very  irregular  and  uncertain 
whatever  their  trade  name,  or  the  manufacturer's  report  of  the  large 
quantities  sold. 

Analysis  of  an  average  brand  of  the  so-called  Portland  cement: 

149 


150  NATURAL  HYDRAULIC   CEMENT. 

Silica (Si02). 20.36  per  cent 

Lime (CaO) 61.90  "  " 

Alumina (AljO8) 7.26  "  " 

Magnesia (Mg.O) 3.10  "  " 

Iron  oxide (Fe.Og) 324  "  " 

Insoluble  residue.. .  .(clay  and  sand)  ...  0.44  "  " 

Sulphur  anhydride . .  (S02) 1.36  "  " 

Carbonic  anhydride  .(C02) 0.33  "  " 

Water (H20) 1.97  "  " 

Soda (Na2O)  )       ,  .  {. 

i.  XT/-  ^  (  h  and  loss. .     0.04    "      " 

Potash (K2O3)  j 

100.00     "      " 

Tensile  strength  of  the  neat  cement  at  the  end  of  7  days  equals 
613  pounds;  at  the  end  of  28  days,  800  pounds;  with  one  part  of 
cement  and  three  parts  of  sand  for  the  same  periods,  228  and  360 
pounds. 

The  composition  of  a  natural-rock  hydraulic  cement  from  Chatta- 
nooga, Tenn.,  is 

Silica 22. 17  per  cent. 

Lime 65.68    "      " 

Alumina 8.20   "      " 

Magnesia 1.45    "      " 

Oxide  of  iron  ..  2.50    "      " 


100.00  < 

It  is  a  natural  Portland  cement  similar  in  character,  but  superior 
to  that  found  at  Boulogne,  France.  The  Chattanooga  deposit  is  in 
the  form  of  layers,  and  is  over  50  feet  thick.  After  calcination  at 
a  white  heat,  the  following  are  the  average  results  from  a  number  of 
tests  of  briquettes. 

After  an  exposure  of  one  hour  in  the  air  and  23  hours  in  water, 
the  tensile  strength  averaged  235  pounds.  After  one  day  in  the  air 
and  6  days  in  water,  623  pounds.  After  one  day  in  the  air  and  27 
days  in  water,  797  pounds.  It  is  the  strongest  natural-rock  cement 
in  the  world. 

Portland  cements  are  commonly  made  from  a  dual  combination 
of  the  following  substances: 

1.  Limestone  with  from  18  to  20  per  cent  of  clay. 


SLAG  HYDRAULIC   CEMENT.  151 

2.  Chalk  and  clay.     Marl  and  clay. 

3.  Clay-bearing  limestone  (argillaceous  limestone)  with  clay,  shale, 
or  slag  sand. 

These  substances  are  pulverized  and  mixed  in  some  proportions 
that  vary  with  the  different  manufacturers.  The  mixture  is  then 
calcined  to  nearly  the  point  of  fusion,  or  to  actual  fusion,  forming  a 
cinder  which  is  finely  pulverized  and  called  Portland  cement. 

Furnace  slag,  the  waste  product  from  blast-furnaces  (see  Analy- 
sis, Chapter  XVI),  is  also  used  as  the  base  of  Portland  cement. 

The  slag  is  heated  in  mass  and  quenched  in  water  to  granulate 
it,  making  slag  sand;  then  dried  and  mixed  with  about  one-fourth 
part  of  slacked  lime,  and  hen  finely  pulverized  to  form  the  cement. 
Slag  sand  usually  contains  from  0.5  to  1.5  per  cent  of  the  sulphide  of 
iron,  that  has  a  tendency  to  oxidize  on  exposure  to  the  air,  which 
action  is  destructive  to  cement  in  above-ground  situations.  Slag 
cements  are  from  6  to  8  hours  in  setting,  as  against  1  to  3  hours  for 
the  American  brands  of  mineral  cements  under  test  of  a  one-pound 
needle. 

The  color  of  slag  cement  is  a  delicate  lilac  or  almost  white.  If 
the  slag  sand  has  been  roasted  prior  to  pulverizing,  it  is  generally 
of  a  dark  color  similar  to  the  ordinary  brands  of  dark  Portland  cement. 
If  a  greenish  color  is  present  in  the  cement,  it  denotes  the  presence  of 
a  large  quantity  of  the  sulphide  of  iron.  This  greenish  color  is  also 
found  in  some  brands  of  the  ordinary  Portland  cement,  where  the 
substances  from  which  it  is  made  contain  iron  sulphide,  and  when 
there  has  been  a  deficiency  of  heat  in  the  oxidizing  flame  of  the  kiln. 

Slag  cements,  when  mixed  and  exposed  to  the  air,  must  be  well 
covered,  else  they  will  crack,  though  they  harden  under  water  without 
swelling  or  any  material  change  in  volume.  They  are  completely 
hydrated  during  the  process  of  manufacture,  do  not  require  aging, 
and  do  not  deteriorate  in  storage. 

The  character  of  furnace  slag  and  all  the  processes  of  its  man- 
ufacture into  cement  require  as  close  attention  to  secure  a  reliable 
product  as  is  required  for  the  mineral  or  Portland  cements.  The 
engineer  should  select  a  cement  for  a  wash  coating  for  ferric  surfaces, 
or  for  a  mortar,  by  its  properties,  not  its  name,  and  should  require 
the  standard  he  desires  to  reach  to  be  met  by  systematic  and  rigid 
tests  of  every  invoice  of  the  cement,  and  many  tests  from  each  in- 
voice, during  their  mixing  and  application,  regardless  of  the  names 
on  the  package 


152  SLAG  HYDRAULIC  CEMENTS. 

The  nature  of  the  cement  has  much  to  do  with  its  effectiveness. 
The  quick-setting  cements  require  the  most  care  in  their  applica- 
tion, and  are  generally  the  best  for  ship  work.  If  the  thin  cement 
wash  once  sets  in  the  bucket  it  will  not  again  set  if  stirred  up — it  is 
then  useless.  Constant  stirring  of  the  paste  is  necessary,  as  fifteen 
to  twenty  minutes  after  mixing  suffices  for  it  to  set  if  not  kept  con- 
stantly stirred. 

The  Portland  cements  set  slower  than  the  American  or  natural 
mineral  cements.  Quicklime  is  sometimes  added  to  delay  the  setting, 
but  renders  the  cement  more  caustic  and  destroys  the  protective 
qualities  of  the  vehicle  in  the  underlying  paint,  and  opens  the  way 
for  moisture  in  the  cement  to  reach  the  metal,  and  all  of  the  coat- 
ings soon  peel  or  flake  off  either  from  the  corrosion  of  the  iron  or 
by  the  destruction  of  the  bond  between  it  and  the  paint. 

Cement  coatings,  unless  spread  where  they  are  freely  exposed  to 
a  circulation  of  the  air,  are  damp,  and  being  porous,  are  not  proof 
against  the  penetration  of  gases  or  liquids.  If  by  accident  they  are 
exposed  to  the  action  of  any  copper  scales,  scrap-metal,  or  water 
charged  with  acid  or  alkaline  substances,  the  soluble  salts  of  copper 
thus  formed  will  penetrate  the  coating,  deposit  the  copper  upon  the 
iron  or  steel  surfaces,  set  up  a  galvanic  action,  and  corrode  the 
metals  beneath  the  cement  coating. 

The  hardness  and  rigidity  of  cement  coatings  render  them  liable 
to  flake  off  the  metallic  surfaces  under  strains  due  to  changes  in  tem- 
perature of  the  metal  that  the  cement  cannot  follow.  Such  places, 
though  of  minor  extent,  are  generally  inaccessible,  and  are  quickly 
corroded:  this  action  being  hastened  by  the  difference  in  potential 
between  the  exposed  metal  and  the  cement  coating,  even  under  ordi- 
nary atmospheric  conditions.  It  is  more  rapidly  developed  if  acidu- 
lated solutions  or  vapors  are  present,  as  they  nearly  always  are  aboard 
ships. 

All  of  these  disadvantages  in  the  use  of  cement  can  with  proper 
care  be  in  a  great  measure  lessened,  if  not  altogether  avoided.  Cement 
coatings  are  in  many  cases  the  only  protection  that  can  be  used  to 
prevent  corrosion,  or  to  arrest  it,  even  where  it  has  progressed  to  an 
extreme  or  dangerous  point. 

Wrought-iron  and  steel  inlet,  stand-pipes,  towers,  and  other  parts 
of  water-works  metal,  are  subject  to  virulent  corrosion.  The  usual 
oil-paint  coatings  are  so  soon  destroyed  by  the  effects  of  water  in 


HYDRAULIC -CEMENT  COATINGS.  153 

motion  as  to  be  nearly  useless;  and  this  is  especially  the  case  if  the 
paint  is  iron  oxide  or  if  it  has  been  spread  over  mill-scale. 

The  collapse  of  many  stand-pipes  shows  in  nearly  every  case  that 
corrosion  was  the  principal  cause  of  their  failure,  as  its  progress  at 
one  or  more  places  had  reached  such  a  degree  that  it  only  needed 
a  small  extraneous  disturbance  to  wreck  the  structure.  A  case  in 
point  is  that  of  the  60-inch-diameter  wrought-iron  inlet-pipes  300 
feet  long,  and  the  lower  sections  of  the  stand-pipe  of  a  large  water- 
works erected  in  1860  and  in  use  only  a  few  years,  when  corrosion 
had  developed  upon  the  inner  surfaces  of  the  pipes  in  so  many  large 
spots  and  blisters,  in  such  an  irregular  manner,  that  the  engineer 
reported  "that  over  one-half  of  the  strength  of  the  pipes  to  resist 
external  pressure  had  been  destroyed.  Parts  of  the  pipes  were  un- 
affected, the  mill-scale  and  shop-marks  being  in  place,  while  nearly 
one-half  of  them  presented  an  appearance  of  being  inoculated  with 
poison." 

The  inlet-pipes  being  buried  in  river-silt  containing  a  large  amount 
of  clay,  were  comparatively  unaffected,  though  below  the  water- 
level;  but  it  was  still  water,  not  subject  to  motion  like  the  suction 
and  force  sides  of  the  pipes. 

The  inside  surfaces  were  scraped  clean  as  possible,  and  then  coated 
with  one  coat  of  neat  hydraulic  cement  from  J  to  f  inch  thick,  laid  on 
by  a  trowel  by  house-plasterers. 

The  water-tower  was  wrecked  by  a  tornado  in  1890,  and  all  the 
pipes  were  found  free  from  rust  in  any  degree,  and  probably  would 
have  lasted  indefinitely. 

Imported  Portland  cement  was  used  on  one  part  of  the  pipes  and 
Louisville  cement  for  the  rest.  The  former  set  slowly  and  had  an 
indifferent  adhesion  to  the  iron.  The  Louisville  cement  set  promptly 
and  was  easier  to  apply. 

Many  other  instances  of  the  successful  use  of  hydraulic  cement  in 
similar  situations  could  be  cited.  The  quality  of  the  cement,  the 
manner  of  mixing  and  applying  it,  and  the  personal  equation  of  both 
the  engineer  and  the  employe,  are  factors  for  success.  Failures  of 
cement  coatings  are  more  frequent  than  successes  for  the  reason  that 
in  their  application  one  or  more  of  these  requirements  have  been 
neglected.*  Prof.  J.  M.  Porter  of  Lafayette  College  divided  a  sam- 


*  "  Notes  on  Cement  Masonry."      By  I.  N.  Knapp,   Gas  Engineers'  Pro- 


154  HYDRAULIC -CEMENT   COATINGS. 

pie  of  a  well-known  and  reliable  Portland  cement  into  nine  parts,  and 
sent  each  to  a  different  physical  laboratory  with  the  request  that  tests 
be  made  of  it  in  a  mortar,  one  part  cement  to  three  of  sand,  according 
to  the  rules  recommended  by  the  committee  of  the  American  Society 
of  Civil  Engineers.  The  resulting  average  strengths  reported  from  each 
of  the  nine  samples  were  as  follows:  75,  102,  114,  136,  153,  163,  176, 
225,  247  pounds  tensile  strength  per  square  inch.  Average  for  all 
the  samples  was  153  pounds,  and  the  lowest  strength  was  but  30  per 
cent  of  the  highest. 

If  these  results  produced  by  experienced  men  in  permanent  labo- 
ratories vary  so  much  with  the  same  cement,  what  is  to  be  expected 
from  the  inexperienced  and  careless  laborers  who  are  generally  em- 
ployed to  mix  and  apply  concrete,  mortar,  or  cement  coatings  ? 

Neat  hydraulic-cement  coatings  crack,  they  set  so  rapidly  that 
there  is  always  a  probability  of  their  setting  before  the  workmen  can 
spread  them,  and  the  tendency  of  the  workmen  to  "knock  them  up" 
when  they  indicate  setting  or  have  set,  instead  of  mixing  a  fresh  batch, 
is  almost  irresistible,  the  result  being  a  coating  of  very  uncertain 
character, — streaks  of  firm  and  close-clinging  cement  alternating  with 
those  of  dead  cement,  that  readily  yield  to  a  slight  change  in  the 
temperature  of  the  metal  or  covered  surface,  or  to  a  slight  mechani- 
cal injury  or  a  frost.  A  strong  heat  from  the  sun  also  causes  them 
to  flake  off. 

Bad  milling  and  insufficient  burning  are  a  frequent  cause  of  poor 
cement,  also  an  excess  of  magnesia  in  the  limestone  or  added  adulter- 
ant. Magnesia  causes  a  chemical  change  or  disintegrating  action  in 
the  cement  when  wetted  in  the  mixing.  Free,  natural  sulphate  of 
lims  is  a  dangerous  impurity.  A  low  specific  gravity  and  a  dark- 
brown  color  are  indicative  of  poor  burning,  and  are  easily  detected. 

For  the  protection  of  iron  or  steel  beams  or  grillage,  laid  as  the 
foundation  or  structure  work  below  the  water-line  to  be  embedded  in 
cement  concrete,  the  metal  should  be  bright  and  free  from  mill-scale, 
which  is  an  electro-negative  element,  and  with  the  moisture  present, 
is  certain  to  produce  a  galvanic  couple  with  the  iron  it  covers  and 
promptly  start  the  corrosion,  that  will  proceed  uninterruptedly  so 
long  as  any  metal  is  left  for  it  to  act  upon.  Every  atom  of  the  red 
rust  as  it  forms,  being  also  electro-negative,  increases  the  galvanic 

ceedings  American  Gas  Association,  New  York  Meeting,  Oct.  16,  1902.  Ameri- 
can Gas  Light  Journal,  Nov.  10,  1902,  pp.  665-673. 


POROSITY  OF  HYDRAULIC  CEMENT.  155 

energy  on  the  remaining  metal.  The  rate  of  this  corrosion  will  prob- 
ably reduce  the  beams  in  less  than  one  hundred  years  to  a  condition 
where  their  strength  to  sustain  any  incumbent  load  will  be  no  greater 
than  an  equal  quantity  of  tan-bark. 

No  paint  coating  on  the  metal  can  resist  the  galvanic  action,  and 
it  should  be  applied  solely  to  prevent  any  slight  corrosion  that  may 
occur  from  the  time  the  metal  is  cleaned  until  it  is  laid  in  situ. 

A  lampblack  and  oil,  or  a  graphite  paint  are  good  anti-corrosive 
coverings,  but  best  of  all  coatings  for  these  situations  is  a  refined 
bitumen  and  dead-oil  mixture  applied  hot.  Oxide  of  iron,  or  any 
other  coating  containing  electro-negative  substances  that  induce 
corrosion  under  atmospheric  conditions,  will  only  add  to  the  strength 
of  the  galvanic  couple,  by  bringing  their  oxidizable  elements  into  the 
field.  The  nature  of  the  soil  in  which  the  metal  is  directly  in  con- 
tact will  also  contribute  to  the  corrosive  action  through  the  galvanic 
couple,  blue  clay  or  solid  rock  only  excepted. 

Concrete,  as  generally  laid,  is  very  porous,  and  is  seldom  so  pro- 
portioned, mixed,  or  rammed  in  place  as  to  enable  it  to  fill  the  voids 
in  its  mass,  and  capillary  action  will  enable  the  moisture  and  soil  acids 
to  reach  the  metal.  In  all  such  foundation  work  the  cement  should 
be  of  the  best  quality,  free  from  sulphur  elements,  the  filler  should 
be  of  small  size,  and  the  sand  absolutely  free  from  salt  or  sea-sand 
in  order  to  minimize  the  dangers  of  corrosion.  These  precautions  are 
seldom  if  ever  taken,  even  in  part,  much  less  as  a  whole.  The  neglect 
of  these  particulars  will  soon  be  apparent  in  the  failure  of  many  an 
important  structure  whose  life  will  be  measured  by  a  few  decades 
instead  of  centuries.  That  the  corrosion  in  these  cases  is  out  of 
sight  and  mind  and  irreparable  will  be  the  more  aggravating. 

Porosity  of  Hydraulic  Cement. 

In  a  general  way,  engineers  and  architects  are  inclined  to  blindly 
trust  hydraulic  cement  in  many  locations  where  in  parallel  cases  it 
has  failed.  The  quality  of  a  cement  suitable  for  a  concrete  block 
would  not  be  advisable  in  a  wash  coating  for  a  wall  or  to  bed  an  anchor 
bar.  All  hydraulic  cements  are  not  only  porous  but  permeable.* 
Quay  walls  laid  in  beton  blocks,  composed  of  about  440  pounds  of 
Portland  cement  to  each  cubic  meter  of  sharp  clean  sand  and  mixed 

*  Excerpts  from  a  Report  of  M.  M.  Leon  Durand  Clave,  Engr.  in  Chief  of 
Bridges  and  Roads,  Paris.  "  Annales  des  Fonts  et  Chausees,"  Mav,  1888. 


156          HYDRAULIC-CEMENT  COATINGS,  ADHESION  OF. 

with  from  300  to  440  pounds  of  water,  the  walls  being  surmounted 
by  ashlar  masonry,  Were  disintegrated  in  less  than  a  year  by  the 
action  of  sea-water.  There  was  a  movement  or  change  in  the  char- 
acter of  the  beton,  even  when  660  to  880  pounds  of  Portland  cement 
per  cubic  meter  of  sand  was  used.  In  parts  of  the  work  where  they 
had  not  been  exposed  to  the  action  of  sea-water,  the  beton  of  all  pro- 
portions of  cement  and  sand  were  not  only  very  porous  but  very 
permeable.  Under  a  head  of  about  three  feet,  the  permeability  was 
indicated  by  a  rapid  fall  of  the  water  in  the  vessel  where  the  beton 
block  was  under  test.  The  permeability  of  the  cement  was  in  all  cases 
accompanied  by  a  disintegrating  effect  in  the  beton.  The  disintegration 
was  found  to  be  due  to  the  formation  of  perceptible  quantities  of  the 
sulphate  of  lime  by  the  action  of  the  sea-wrater  on  the  Portland  cement,, 
The  sulphate  of  lime,  when  formed  in  the  mass  of  concrete,  solidified 
more  or  less  completely  in  crystals  of  such  a  nature  as  to  develop  con- 
siderable molecular  activity.  Some  of  the  beton  cement  analyzed 
.75  to  .80  per  cent  of  sulphuric  acid. 

The  greater  the  amount  of  water  used  to  mix  the  cement  the  greater 
was  the  permeability  and  porosity  of  the  concrete,  even  with  all  pro- 
portions of  the  cement  and  sand.  Mortar  made  with  7  per  cent  of 
water  was  very  permeable,  and  this  increased  perceptibly  as  the  per- 
centage was  increased  to  ten  and  eleven.  In  all  cases  where  sea- 
water  instead  of  fresh  water  was  used  to  gauge  the  cement,  the  bad 
effects  in  the  mortar  were  at  once  apparent. 

Prof.  Bauschinger's  experiments  showed  that  the  adherence  of  a 
first-class  Portland  cement  to  a  bright  wrought-iron  floor  beam  was 
625  pounds  per  square  inch;  that  mixtures  of  two  parts  of  fine, 
sharp  bank  sand  to  one  of  cement  reduced  the  adhesion  to  about  70 
per  cent  of  the  above  value.  In  mixtures  of  three  parts  of  sand  to 
one  of  cement  the  adhesion  value  was  less  than  50  per  cent.  That 
with  each  increase  in  the  percentage  of  sand  from  the  above  amounts, 
the  reduction  in  strength  and  adhesion  was  very  rapid.  The  quality 
of  the  cement  had  a  great  effect  upon  the  adhesion  value.  In  the 
commercial  cements  usually  provided  for  contract  concrete,  the  adhe- 
sion was  "requently  only  20  per  cent  of  that  given  above. 

Bloxam's  " Chemistry,"  edition  1895,  pp.  376,  377,  states  "that 
the  ordinary  corrosion  of  iron  is  accomplished  only  in  the  presence  of 
moisture,  air,  and  CO2.  If  any  of  these  substances  are  absent  the 
corrosion  cannot  take  place.  The  reactions  are: 

Fe+H2O+CO2  =  FeCO3+H2.       .  '.     .     .         (a) 


HYDRAULIC-CEMENT   COATINGS,  DEFECTS  OF.  157 

The  FeCO3  is  dissolved  by  the  carbonic  acid  present,  and  the  solution 
absorbs  oxygen  from  the  atmosphere,  in  accordance  with 


2FeCO3+O  =  Fe2O3+2CO2. 


The  Fe2O3  combines  with  the  moisture  and  is  deposited  as 
2Fe203.3H2O,  or  ordinary  iron  rust.  Iron  in  its  ordinary  state  is 
not  affected  in  perfectly  dry  air,  and  it  will  not  rust  in  water  con- 
taining a  free  alkali  or  alkaline  earth  or  an  alkaline  carbonate, 
because  the  affinity  of  these  alkaline  substances  for  any  acid  is 
greater  than  that  of  iron,  so  that  they  would  neutralize  the  acid 
before  it  had  time  to  attack  the  iron." 

This  neutralizing  action,  however,  would  only  be  effective  for  a 
short  time  or  until  the  alkaline  substance  became  saturated  with  the 
acid  element.  There  are  no  locations  where  concrete  is  used  or  cement 
coatings  applied  to  iron  for  its  protection  from  corrosion  where  reviv- 
ing the  saturated  alkaline  substance  is  possible.  It  is  therefore  only 
necessary  to  have  a  limited  amount  of  some  acid  present  with  air  and 
moisture  to  cause  the  ultimate  destruction  of  a  large  amount  of  iron, 
because  the  C02  or  other  acids  present  never  become  fixed,  but  are 
always  active,  passing  from  molecule  to  molecule,  as  long  as  there  is 
any  free  metal  for  them  to  attack. 

It  is  proposed  to  increase  the  safeguard  afforded  by  alkaline  sub- 
stances to  delay  corrosion  by  mixing  the  concrete,  mortar,  or  wash 
coating  with  whitewash  instead  of  plain  water.  The  small  amount 
of  lime  thus  added  to  the  cement  does  not  materially  detract  from  its 
strength. 

Slag  cements,  because  of  the  sulphides  present,  should  be  avoided 
for  use  in  concrete  or  any  coatings  in  contact  with  iron.  It  is  hardly 
possible  to  assemble  them  with  an  amount  of  any  alkaline  substance 
that  will  permanently  neutralize  the  acid  element  present  in  their 
composition,  aggravated  in  nearly  every  instance  by  the  porous  nature 
of  all  concrete  constructions  caused  by  deficient  ramming  to  fill  the 
voids  occupied  by  the  enclosed  air,  also  by  the  surplus  of  water  used 
in  mixing. 

Even  a  cement  free  from  the  sulphur  element,  if  mixed  with  a 
small  quantity  of  cinder,  or  if  laid  in  soil  containing  cinders  or  pyrites, 
will  absorb  the  acid  and  collect  it  in  dangerous  amounts  in  the  voids 
of  the  concrete.  Once  there,  it  will  ultimately  reach  the  metal  and 
cause  the  failure  of  the  grillages  by  the  columns  or  other  superincum- 
bent load  punching  through  the  foundations.  These  conditions  are 


158  CORROSION  OF  STEEL  IN  CONCRETE. 

further  aggravated  by  the  fact  that  nearly  all  ground-water  is  charged 
to  some  extent  with  saline  or  sulphur  elements  or  both,  that  would 
soon  saturate  any  alkaline  substance  present  in  the  cement.  When 
this  point  is  reached  corrosion  of  the  grillage  will  inevitably  ensue 
even  if  the  imposed  columns  show  no  evidence  of  its  action. 

Grillage  ironwork  has  been  removed  from  concrete  foundations 
laid  only  five  years  and  found  to  be  corroded  £  inch  or  more  over  its 
whole  surface.  The  .thickness  of  grillage  beams  is  seldom  ^  inch,  so 
that  thirty  or  fifty  years  will  practically  limit  the  safety  of  many  of 
the  modern  steel  skeleton  structures. 

The  protection  afforded  to  steel  by  Portland  cement  has  been  sub- 
jected to  experiment  by  Prof.  Charles  L.  Norton.*  "Two  brands  of 
American  cement  were  selected,  tested  chemically  and  physically  and 
found  to  be  good.  A  sharp,  clean  bank  sand  and  fragments  of  trap- 
rock  and  flint  were  thoroughly  washed  and  used  for  the  concrete. 
The  cinders  were  washed  and  dried;  they  tested  distinctly  alkaline 
with  a  small  amount  of  sulphur.  All  the  ingredients  were  mixed  dry 
in  every  case,  and  when  wet  with  a  minimum  amount  of  water  were 
tamped  until  they  flushed. 

"  Briquettes  were  made  in  duplicate  with  both  cements>  viz.,  neat 
cement,  one  part  to  three  of  sand,  one  part  to  five  of  broken  stone; 
cement  one  part,  two  of  sand,  and  five  of  stone;  cement  one  part,  sand 
two  parts,  and  five  of  cinders.  Specimens  of  mild-steel  rods  6"  +  ^" 
diameter,  mild  sheet-steel  plates  6"+l"+¥y  thick,  and  strips  of  ex- 
panded metal  6"+  1"  were  all  cleaned  bright.  All  three  pieces  were 
put  into  each  briquette  and  were  enclosed  in  separate  tin  boxes,  which 
also  contained  a  specimen  of  each  metal  unprotected.  One-half  of 
the  briquettes  were  set  in  water  for  one  day  and  the  rest  for  seven 
days  before  sealing  them  up  tight.  One-quarter  of  the  boxes  were 
then  subjected  to  each  of  the  following  exposures.  To  an  atmos- 
phere of  steam,  air  and  carbon  dioxide;  to  air  and  steam;  to  air  and 
carbon  dioxide,  and  the  other  samples  set  upon  a  table  in  a  room  with 
no  special  care  as  to  their  temperature  or  dryness. 

"At  the  end  of  three  weeks  the  briquettes  were  cut  open  and  the 
steel  examined  and  compared  with  the  specimens  which  had  lain 
unprotected  in  each  of  the  tin  boxes. 

"  The  specimens  covered  with  neat  cement  were  as  bright  as  when 
placed  in  the  briquette,  the  cement  had  prevented  any  trace  of  corro- 

*  Engineer  in  charge  of  the  Insurance  Engineering  Experiment  Station, 
31  Milk  Street,  Boston,  Mass.  Excerpts  from  Third  Report,  1902. 


CORROSION  OF  STEEL  IN  CEMENT.  159 

sion,  while  the  unprotected  samples  consisted  of  more  rust  than  steel. 
Of  the  remaining  specimens  hardly  one  had  escaped  serious  corrosion. 
The  location  of  the  rust  spot  was  invariably  coincident  with  either  a 
void  in  the  concrete  or  a  badly  rusted  cinder.  Rust  had  as  usual  pro- 
duced rust. 

11  In  the  more  porous  mixtures  the  steel  was  spotted  with  alternate 
bright  and  rusty  areas,  each  clearly  defined.  In  both  the  solid  and 
porous  cinder  concrete  many  rust  spots  w^ere  found,  except  where  the 
concrete  had  been  mixed  very  wet,  in  which  case  the  watery  cement  had 
coated  nearly  the  whole  of  the  steel  like  a  paint  and  protected  it. 

"Some  briquettes  made  of  finely  ground  cinders  and  cement  in 
varying  proportions  up  to  one  of  cement  to  ten  of  cinders  and  exposed 
to  moisture  and  carbonic  acid  showed  how  effectually  the  presence  of 
the  cement  prevented  rusting,  provided  there  were  no  cracks  or  crev- 
ices or  distinct  voids.  The  corrosion  found  in  cinder  cement  appeared 
to  be  mainly  due  to  the  iron  oxide  in  the  cinders  and  not  to  the 
sulphur.  Cinder  concrete,  well  rammed  when  wet  to  fill  the  voids, 
is  about  as  effective  as  stone  concrete  in  protecting  steel." 

These  latter  conclusions  would  depend  greatly  upon  the  absence 
or  low  percentage  of  iron  oxide  and  sulphur  in  the  cinder.  To  render 
these  elements  inert  to  iron,  there  must  be  enough  free  alkaline  sub- 
stance in  the  cement  to  saturate  the  acids  without  disturbing  the 
general  composition  of  the  cement  as  a  binding  element. 

If  the  metal  is  painted  before  the  application  of  the  concrete,  what- 
ever its  composition,  the  continuous  void  left  over  the  whole  surface 
of  the  metal  by  the  decay  of  the  paint  is  the  best  possible  condition 
for  inaugurating  corrosion.  Air  and  moisture  will  find  ready  access 
to  this  void,  also  to  the  voids  left  by  building  bricks  and  terra-cotta 
blocks,  the  porous  nature  of  which  are  favorable  to  the  condensation 
and  absorption  of  moisture  and  atmospheric  gases,  that  are  more 
highly  charged  with  corrosive  elements  in  cities,  tunnels,  subways,  and 
other  locations  where  the  use  of  structural  steel  work  is  in  most  de- 
mand. 

How  far  the  protection  of  ferric  foundations,  either  near  or  below 
the  water-line  in  the  many  structures  already  built,  or  in  progress  in 
all  parts  of  the  world,  has  been  considered  by  their  architects  and 
engineers  time  only  will  reveal.  For  those  proposed,  like  the  miles 
of  "rapid  transit  and  railway  tunnels,  a  great  portion  of  which  will  be 
carried  through  ocean  silt  or  salt-marsh  mud  and  exposed  to  the  most 


160  CEMENT  FOR   TUNNEL  WORK. 

virulent  form  of  corrosion,  some  more  positive  and  effectual  means  of 
protection  from  corrosion  must  be  employed  than  has  ever  been 
adopted.  No  wash  or  trowel  coating  of  cement,  good  or  bad,  or 
applied  in  mass,  will  avail  for  but  a  short  period  to  protect  the  metal 
that  these  structures  must  rely  upon  for  a  great  part  of  their  strength. 

The  hardness  and  inelastic  character  of  cement  or  mortar  coatings 
will  cause  them  to  crack  under  the  vibrations  inevitable  to  all  rail- 
way structures;  and  while  resisting  water  in  mass,  they  will  absorb 
moisture  sufficient  to  be  always  damp  and  in  that  condition  are  of 
the  least  strength. 

The  wires  of  the  anchorage  ends  of  the  cables  of  the  Niagara  Falls 
suspension  bridge  were  opened  for  a  short  distance  where  they  entered 
the  anchorage  pits.  These  ends  were  embedded  in  hydraulic  cement, 
and  at  the  end  of  forty  years  many  of  them  had  become  so  corroded 
that  the  strength  of  the  structure  was  seriously  impaired.  The  cor- 
roded strands  were  replaced  by  new  wires,  and  the  top  part  of  the 
anchorages  opened  to  allow  the  cement  work  to  dry  out  and  remain 
dry.  In  this  case  and  with  all  ferric  material  embedded  in  concrete, 
the  caustic  action  of  the  usual  make  of  cement,  whether  damp  or 
wet,  will  furnish  the  carbonic  acid  necessary  to  destroy  any  linseed- 
oil  coating  or  paint  that  covers  them  and  induce  corrosion.  The 
subsequent  drying  out  of  the  cement  coverings  only  delays  for  a 
short  time  the  ultimate  destruction  of  the  metal. 

Iron  anchor  bars  and  chains  embedded  in  concrete  below  the  water- 
line  for  100  and  200  years  were  free  from  rust  when  removed.  Fresh- 
water immersion,  no  access  of  air,  no  acid  element  nor  iron  oxide  or 
calcium  sulphate,  also  no  voids  in  the  cement  was  the  secret  of 
their  perfect  condition. 

The  present  method  of  constructing  buildings  wholly  or  in  part  of 
steel  framing  and  concrete,  avoiding  the  use  of  brick  and  stone  ma- 
sonry as  far  as  possible,  is  causing  a  great  deal  of  anxiety  among  archi- 
tects and  engineers  as  to  the  future  state  of  'the  metal  so  embedded. 
That  metal  needs  some  additional  protection  from  the  caustic  action 
of  the  impure  cements  too  frequently  employed,  also  from  the  quick- 
lime mortar,  beyond  the  usual  coat  of  paint,  is  recognized. 

At  a  late  meeting  of  the  English  Architectural  Association,  Mr. 
H.  Humphrey  gave  as  the  result  of  his  experience  that  metal  buried 
in  concrete  containing  furnace  cinders  or  coke  breeze,  should  be 
coated  with  Dr.  Angus  Smith's  anti-corrosive  compound,  or  some 


CINDER  IN  CEMENT  COATINGS.  161 

other  compound  containing  pitch  and  sand;  that  some  samples  of 
cinder  concrete  analyzed  as  high  as  three-fourths  of  one  per  cent  of 
sulphuric  acid.  A  case  was  cited  by  another  member  of  the  asso- 
ciation where  a  hot-water  pipe  laid  in  cinder  concrete  was  rotted 
away  in  a  very  short  time. 

The  cinder  concrete  used  in  the  floors  of  the  steel-frame  sky- 
scrapers in  New  York  City  invariably  shows  the  presence  of  sul- 
phuric acid  strong  enough  to  redden  litmus-paper. 

Gas-pipes  embedded  in  plaster  of  Paris  (gypsum)  have  been  found 
to  be  completely  corroded  in  a  few  years.  The  use  of  gypsum  in 
cement  to  hasten  its  setting  is  detrimental.  Gypsum  is  soluble  to 
some  extent  in  water,  besides  it  contains  water  from  its  hydration, 
which  absorbs  carbonic  acid  from  the  air  that  quickly  causes  corro- 
sion. The  rust  so  formed  absorbs  moisture  and  carbonic  acid  and 
further  hastens  the  corrosion. 

The  screwed  ends  of  all  pipes  are  invariably  attacked.  They  are 
of  bright  metal  only  about  yV  inch  thick  and  seldom,  if  ever,  have 
even  a  brush  coating  of  any  paint  to  protect  them  when  put  up  or 
left  in  place.  Galvanizing  the  fittings  and  body  of  the  pipes  does 
not  protect  the  screwed  ends;  the  corrosion  at  these  points  is  only 
hastened  by  the  galvanizing. 

The  effect  of  corrosion  upon  the  floor  beams  and  other  structural 
parts  used  in  modern  architectural  work  has  been  the  subject  of  dis- 
cussion by  the  American  Society  of  Architects,  the  concensus  of  their 
opinion  being  expressed  by  one  of  the  prominent  members  as  follows: 

"  With  regard  to  the  strength  of  the  steel-cage  constructions,  both 
as  to  wind  strain  and  other  disturbing  strains,  there  is  no  question. 
All  objections  arising  from  these  points  have  been  overcome,  but  un- 
less exceptional  care  is  taken  in  the  construction  to  protect  the  steel 
cage,  particularly  at  its  joints,  from  corrosion,  this  class  of  buildings 
will  not  be  permanently  safe.  It  is  perfectly  feasible,  with  great 
care,  to  protect  the  steel  frames  from  corrosion,  but  I  am  convinced 
that  many  high  buildings  have  been  put  up  in  this  country  where  the 
proper  care  in  this  respect  has  not  been  taken  nor  the  necessary 
preventives  against  corrosion  applied." 

On  the  12-inch  steel  I  beams  carrying  the  sidewalks  around  the 
Pabst  Hotel  in  New  York  City,  and  that  were  removed  after  being  in 
place  less  than  six  years,  corrosion  was  in  active  progress.  The 
space  beneath  the  beams  was  used  as  a  cafe,  always  dry  and  heated. 


162  CEMENT  COATINGS  FOR  MARINE  WORK. 

Wherever  the  brickwork  came  in  contact  with  the  beams  in  all  of  the 
stories,  the  paint  was  dead  and  corrosion  established.  This  was  par- 
ticularly noticeable  in  many  portions  of  the  beams  where  the  usual 
top  dressing  of  coal  cinders  had  been  laid  to  level  up  the  arches  form- 
ing the  foundation  for  the  artificial  stone  sidewalk.  The  rivets  that 
held  the  corner  angle-irons  to  the  beams  were  nearly  all  loose  from 
the  corrosion  around  their  heads  or  points  and  had  lost  their  set  or 
draw. 

In  marine  work,  hydraulic  cement  is  used  almost  exclusively  as  a 
brush  coating  on  the  inside  surfaces  of  the  ship's  frames  and  plating 
in  the  lower  holds  of  the  vessel  where  the  metal  is  exposed  to  the 
action  of  bilge- water,  alkaline  and  acid  solutions  from  acids,  and 
leakage  from  the  cargo  liquids.  One  or  more  wash  coatings  of  cement 
are  applied  over  the  red-lead,  black-varnish,  or  other  oil-paint  coating 
laid  on  during  the  construction  of  the  ship,  and  that  generally  serve 
to  protect  the  metal  during  this  period.  The  coatings  in  the  lower 
part  of  a  ship  are  damp  by  reason  of  the  confined  saturated  sea  air, 
but  the  cement  (if  good)  forms  a  close,  clinging  coating  that  seldom 
fails  unless  by  mechanical  injury  or  impropei  mixing  or  application, 
and  is  easily  repaired  if  injured. 

The  confined  spaces  aboard  a  ship  almost  preclude  the  use  of  an 
oil  paint  or  varnish,  however  quick  drying  it  may  be,  without  the  use  of 
forced  ventilation  to  provide  the  oxygen  necessary  in  the  drying  of 
paint.  Such  ventilation  is  practically  impossible  in  a  ship  at  sea, 
or  in  most  cases  in  dry  dock. 

Cement  for  rendering,  with  the  object  of  making  brickwork  water- 
tight, should  be  mixed  with  an  equal  part  of  absolutely  clean  sand  free 
from  salt  or  sea-sand.  Cement  for  any  use  should  be  carefully  turned 
over  by  the  shovel  and  exposed  to  the  air  before  being  mixed  or 
wetted. 

Brickwork  is  one  of  the  worst  surfaces  to  hold  a  paint,  good  or 
poor.  A  hard-burnt  brick  will  absorb  8  ounces  of  water,  a  salmon 
brick  nearly  11  ounces.  Brickwork  absorbs  most  of  the  oil  in  the 
paint,  leaving  the  pigment  on  the  surface  of  the  bricks  without  suffi- 
cient bond  to  hold  it,  and  it  peels  in  strips.  This  peeling  is  hastened 
by  the  caustic  action  of  the  cement  or  lime  mortar  and  the  soluble 
salts  in  the  sand  of  the  mortar,  which  soon  destroys  the  organic  mat- 
ter in  the  oil. 

The  soluble  salts  in  the  bricks  and  mortar  often  cause  a  white 
efflorescence  to  appear  on  the  surface  of  the  wall  shortly  after  being 


PAINTING  OF  BRICK  WALLS.  163 

built.  This  cannot  be  brushed  off,  but  it  disappears  during  wet 
weather  and  returns  again  when  the  wall  is  dry,  and  is  only  dissipated 
after  many  rain-storms.  The  composition  of  the  efflorescence  varies. 
The  chlorides  of  calcium,  magnesium,  and  sodium  sulphate  and 
oxalate  of  lime  are  generally  present;  all  of  which  are  hygroscopic 
and  form  a  germinating  place  for  fungi,  one  of  which,  the  Penicilium 
crustaceum,  is  represented  by  Fig.  24.* 

Walls  a  year  or  more  old  are  less  troubled  with  the  efflorescence 
or  by  the  peeling  of  the  paint  from  the  fungus. 


FIG.  24. — Photomicrograph  X  600  of  Penicilium  crustaceum.     This  is  the  greenish 
fungus  which  makes  calcium  oxalate  on  brick  walls.     (M  Toch.) 

When  walls  are  freshly  laid  or  plastered  the  surfaces  can  be  pre- 
pared for  pain  ting- by  applying  a  solution  made  of  twelve  fluid  ounces 
of  sulphuric  acid  in  a  gallon  of  water  and  repeating  the  application 
when  the  first  one  appears  dry.  Allow  the  coatings  to  stand  for 
a  day  or  two,  then  rinse  off  with  clear  water,  and  when  dry  prime 
and  paint  as  usual.  This  process  changes  the  lime  in  the  mortar  and 
cement  from  a  caustic  carbonate  to  a  neutral  sulphate  of  lime;  also 
produces  a  uniformly  absorbent  surface  free  from  spots  that  are  more 
porous  than  the  general  surface,  or  that  contain  lumps  of  improperly 
slaked  or  mixed  lime.  The  surface  so  prepared  takes  the  paint  easily 
and  well  and  does  not  blister  nor  peel. 

If  plastered  surfaces  a  few  months  old  be  washed  with  a  solution 

*  Maximilian  Toch  (New  York  City).  Journal  of  Chemical  Industry  (London), 
Vol.  XXI,  No.  2,  Jan.  31,  1902. 


164  PAINTING  OF  BRICK  WALLS. 

of  2  ounces  of  bicarbonate  of  ammonia  in  a  gallon  of  water,  as  soon 
as  dry  the  oil  priming  or  painting  can  be  done  without  danger  of 
peeling. 

A  silicate  of  soda  solution  made  from  equal  weights  of  silicate  and 
warm  water,  and  applied  with  a  brush,  is  also  recommended  for  pre- 
venting the  peeling  of  paint  on  walls,  but  for  outside  exposures  it  is 
not  so  effective  as  the  above  acid  treatment. 

Waterproofing  Bricks  and  Sandstone.  At  a  recent  meeting  of  the 
Australian  Association  for  the  Advancement  of  Science,  Professor 
Liversidge  read  a  paper  on  the  "  Waterproofing  of  Brick  and  Sand- 
stone with  Oils."  Experiments  were  made  with  the  view  of  ascertain- 
ing the  length  of  time  that  brick  and  sandstone  are  rendered  water- 
proof or  protected  by  oil.  The  oils  used  were  the  three  commonest 
and  most  readily  obtainable  for  such  purposes,  viz.,  linseed-oil,  boiled 
linseed,  and  the  crude  mineral  oil  known  as  "blue  oil,"  used  for  pre- 
serving timber.  The  weatherings  were  made  upon  a  flat  portion  of 
the  laboratory  roof  fairly  exposed  to  the  sun  and  weather.  Good, 
sound,  machine-made  bricks  were  experimented  on.  The  amount  of 
oil  and  water  taken  up  by  the  sandstone  was  very  much  less  than 
that  absorbed  by  the  brick,  although  the  area  of  the  sandstone  cubes 
was  much  greater  than  that  exposed  by  the  bricks.  Equal  amounts 
of  raw  and  boiled  oils  were  absorbed ;  the  blue  oil,  however,  was  taken 
up  in  much  greater  quantity  by  both  brick  and  sandstone,  but  by  the 
end  of  twelve  months  the  whole  of  the  13£  ounces  of  blue  oil  had 
apparently  evaporated  and  the  brick  had  returned  to  its  original 
weight.  The  bricks  treated  with  raw  and  boiled  oils  remain  unchanged. 
After  the  second  oiling  in  November,  1890,  and  exposure  for  nearly 
four  years  and  two  months,  they  had  practically  retained  all  their  oil, 
inasmuch  as  they  had  not  lost  weight,  and  were  also  nearly  impervious 
to  water.  It  was  noticeable  that  the  sandstone  cubes  treated  with 
raw  and  boiled  oils  returned  to  their  original  weights,  but  did  not 
appear  to  have  lost  the  beneficial  effects  of  the  oils,  being  also 
practically  waterproof. 

Portland  or  other  hydraulic  cements  free  from  the  sulphate  of  lime, 
when  mixed  with  about  15  to  25  per  cent  of  a  red-lead  paint,  forms  a 
tough  elastic  coating  that  dries  hard  enough  to  resist  the  action  of 
locomotive  exhaust  steam  and  cinders  on  the  surfaces  of  iron  beams, 
trusses,  and  the  buckle-plates  of  low  headway  bridges.  It  is  also 
damp-resisting  to  a  great  degree,  and  can  be  coated  over  with  other 
paints  with  some  measure  of  confidence  that  they  will  not  peel. 


PAINTING  OF  BRICK  WALLS.  165 

A  special  damp-resisting  paint,  known  as  the  "R.  I.  W."  (trade- 
mark), has  proven  of  merit  in  many  instances  of  its  use  in  very  un- 
favorable situations.  From  a  government  analysis  of  it,  the  com- 
position is  approximately  30  per  cent  of  an  oil  vehicle,  65  per  cent 
of  refined  special  bitumen  and  selected  fossil  resins,  and  5  per  cent  of 
a  carbon  pigment.  It  is  laid  on  or  spread  like  a  thin  coating  of  mortar 
on  brick  masonry  or  plastered  walls.  It  adheres  firmly,  becomes  very 
tacky,  and  can  be  plastered  over  with  cement  or  lime-mortar  coatings 
that  adhere  firmly.  When  these  plastered  coatings  are  dry  they  can 
receive  an  oil  paint  of  any  desirable  color,  unaffected  by  dampness 
from  the  walls. 

A  grade  of  the  "R.  I.  W."  is  also  made  to  apply  to  damp  walls  not 
intended  to  be  plastered,  also  to  iron  structural  work.  This  is  applied 
with  a  brush,  and  contains  more  pigment  than  the  trowel  grade.  It 
is  thoroughly  damp-proof,  and  receives  oil-paint  coatings  without  any 
tendency  to  craze  them  or  to  peel. 

A  grade  of  this  composition,  to  be  spread  with  a  brush  on  the  inside 
of  tanks  where  acid  and  alkaline  solutions  are  stored,  effectually  resists 
the  action  of  these  liquids.  In  chemical  works  for  the  protection  of 
the  ironwork  and  other  metals,  it  has  shown  great  resisting  power. 
A  special  instance  of  the  waterproofing  character  of  this  compound 
to  resist  the  action  of  running  water  under  a  considerable  head  is  on 
the  concrete  monolithic  water-power  house  on  the  St.  Lawrence  River 
at  Massena,  N.  Y.,  where  several  thousand  square  yards  each  of  the 
trowel  and  brush  coatings  were  applied,  and  completely  corrected  the 
porosity  and  permeability  of  the  cement  walls  that  were  seriously  en- 
dangering the  structure. 

Herr  Wm.  Cremer,  superintendent  of  the  gas-works  at  Enskirchen, 
Germany,  states:  "That  the  ammoniacal  liquor  from  gas-works,  even 
in  the  weakest  solutions,  detrimentally  affects  the  cement  and  tank- 
walls  exposed  to  its  action.  Coating  the  surfaces  thus  exposed  with 
liquid  glass  (tungstate  of  soda)  protects  the  cement,  also  renders  the 
surfaces  quite  leakage-proof  even  in  very  old  work." 


CHAPTER  XVI. 

BOWER-BARFF  COATINGS. 

"  Bower-Bar ff  "  is  the  name  given  to  the  rustless  coating  formed 
upon  cast  iron,  wrought  iron,  and  steel,  when  exposed  to  a  low  red 
heat  in  special  ovens,  furnaces,  or  retorts,  and  subjected  to  the  action 
of  superheated  steam,  carbonic-oxide  gas  from  coal-fires  or  gas-pro- 
ducers, hydrocarbon  and  hydrogen  gas  alternately  or  in  combina- 
tion, according  to  the  several  processes  invented  by  Bower-Barff, 
Wells,  Gesner,  and  other  inventors. 

The  original  inventor  of  the  rustless  iron  coating  was  Prof.  Fred- 
erick S.  Barff,  of  Kilburn,  England,  who  published  an  account  of  his 
process  in  1876,  and  read  a  paper  describing  it  before  the  Society  of 
Arts,  London ;  but  the  process  did  not  prove  commercially  successful 
on  account  of  its  high  cost  and  the  difficulty  of  obtaining  uniformity 
in  results. 

Messrs.  George  and  Anthony  Bower,  of  St.  Neats,  England,  im- 
proved the  process  of  Prof.  Barff,  and  patented  it.  The  right  to  use  it 
in  the  United  States  was  acquired  by  Mr.  George  W.  Maynard,  of  New 
York.  The  first  furnace  was  erected  at  the  Hecla  Architectural  Iron 
Works,  in  Brooklyn,  N.  Y. 

The  next  and  most  important  of  the  improvements  in  this  process 
was  invented  and  patented  in  1888  by  Mr.  W.  T.  Wells,  of  Little  Ferry, 
N.  J.,  who  discovered  that  red-hot  iron,  in  the  presence  of  mingled 
steam  and  carbonic  oxide,  would  form  the  magnetic  or  black  oxide 
(rustless  coating)  of  iron,  Fe3O4,  without  the  intermediate  formation 
of  the  sesquioxide,  Fe3O2  (red  rust),  the  reactions  being,  3Fe+4H20. 
=Fe3O4-f  4H2.  This  process  is  the  foundation  for  all  subsequent  im- 
provements of  the  process  and  is  applicable  to  all  forms  of  cast,  mal- 
leable, wrought  iron,  and  steel  where  the  surfaces  are  not  to  be  sub- 
jected to  hard  friction  or  wear,  such  as  bending,  hammering,  chipping, 
or  other  rough  usage. 

The  protection  of  the  metal  being  due  to  the  conversion  of  the 
surface  of  the  metal  to  magnetic  oxide,  and  not  any  material  altera- 

166 


BOWER-BARFF  COATINGS.  167 

tion  of  the  metal  which  would  weaken  it,  it  follows  that  any  manipu- 
lation that  would  injure  the  continuity  of  the  coating  must  neces- 
sarily destroy  the  coating.  Wherever  the  coating  is  broken  the  metal 
will  rust,  though  the  rust  will  be  localized,  and  will  be  greater  than  the 
same  exposure  of  the  metal  not  coated,  owing  to  the  difference  in 
potential  between  the  two  surfaces. 

These  rust-spots  seldom  spread  or  raise  the  adjacent  coating,  as 
is  commonly  the  case  with  paint,  or  enamelled  coatings.  All  drilling, 
fitting,  screw-cutting,  etc.,  of  the  metal  should  be  done  before 
it  is  put  into  the  converting-oven.  In  riveting,  the  oxide  in  the 
immediate  neighborhood  of  the  rivets  will  be  broken,  and  bolting 
together  of  parts  to  be  connected  together  must  be  substituted.  In 
work  that  is  riveted  up  before  being  coated,  the  set  or  draw  of  the 
rivets  will  be  released  by  the  heat  of  the  furnace.  This,  in  the  case  of 
light  grill,  lattice,  or  fence  work,  is  possibly  of  small  moment,  but  in 
work  subject  to  the  action  of  liquids  or  gases  it  cannot  be  ignored 
and  other  methods  of  joining  the  pieces  must  be  adopted.  Shear- 
ing, flanging,  sharp  bending,  or  driving  of  nails  through  sheet-iron 
roofing,  necessarily  exposes  the  metal,  and  local  corrosion  of  the  in- 
jured part  follows.  The  bite  of  the  vise  or  pipe-wrench  in  fitting 
rustless  screwed  steam-  or  water-pipes  injures  the  coating  unless 
special  care  and  tools  are  used  to  prevent  the  injury.  The  screwed 
ends  of  pipes  and  fittings  are  injured  if  the  joints  are  made  up  dry, 
but  with  red  lead,  graphite,  or  other  good  pipe-joint  cements  as  lubri- 
cants, they  seldom  give  trouble  if  moderate  care  is  exercised  in  the 
work. 

In  cast-iron  pipe  with  bell  and  spigot  joints,  the  lead  packing  can 
be  calked  without  injury  to  the  " rustless"  coating  by  using  the  round- 
nose  calking-tool,  instead  of  the  usual  sharp-edged  tool  that  chips  the 
coating.  Rustless  pipe  coatings  do  not  appear  to  draw  in  the  lead 
joint  any  more  than  the  usual  coal-tar  dip  coatings,  from  the  changes 
in  temperature  that  all  pipes  are  subjected  to  when  buried  in  the 
ground. 

The  mechanical  finish  of  the  metal  to  be  coated  determines  to  a 
great  extent  the  mode  of  treatment.  Articles  in  the  rough,  from 
which  the  skin  has  not  been  removed,  require  a  longer  exposure, 
higher  heat,  and  a  more  energetic  oxidation  than  those  whose  sur- 
faces are  more  or  less  machined  or  finished ;  the  latter  requiring  lower 
heats.  A  high  heat  on  a  finished  surface  tends  to  blister  and  detach 
the  oxide  as  fast  as  it  forms.  Ordinarily,  only  the  rust  and  mill- 


168  BOWER-BARFF  COATINGS. 

scale  are  removed  by  scraping  and  use  of  steel  brushes.  Where  a 
handsome  appearance  of  the  oxidized  ware  is  desired,  the  surfaces 
must  be  cleaned  by  the  sand-blast,  or  by  pickling,  and  the  same  care 
used  to  remove  all  traces  of  the  pickling  acid  by  a  warm  lime-water 
bath  and  repeated  washing  with  cold  water- jets  under  pressure,  as 
in  the  case  of  cleaning  the  metal  for  painting  (Chapter  XXVIII). 
Foundry-sand  upon  castings,  if  not  removed,  bakes  in  the  furnace 
to  a  reddish-brown  color,  producing  unsightly  spots,  but  does  not 
impair  the  rustless  character  of  the  coating,  and  unless  the  coating 
is  to  serve  as  a  finish,  without  being  painted,  the  spots  are  of  no 
moment;  otherwise  the  sand  must  be  removed  to  the  clean-scale 
surface  before  treatment.  All  blow-holes  and  other  defects  in  cast- 
ings must  be  plugged  with  brass  or  iron  plugs.  Lead  or  other  soft 
fillings  are  detrimental  to  the  action  of  the  furnace  in  producing  a 
reliable  or  fine-appearing  coating,  which  should  be  a  pleasing  blue- 
gray  or  blue-black  color.  If  the  metal  is  polished  before  treatment, 
it  acquires  a  lustrous  ebony-black  finish,  very  desirable  upon  certain 
kinds  of  articles. 

The  iron  or  steel  articles  treated,  owing  to  the  annealing  action 
while  in  the  furnace,  are  permanently  expanded  about  -^  inch  per  foot, 
for  which  allowance  must  be  made  where  this  addition  will  be  repeated, 
as  in  stair-stringers,  columns,  etc. 

The  limit  of  elasticity  of  the  oxide  coating  is  practically  the  same 
as  that  of  the  metal  it  covers.  The  coating  adheres  firmly  under 
tensile,  torsion  and  compressive  strains,  until  the  elastic  limit  has  been 
reached,  and  no  further. 

In  Sir  Joseph  Whitworth's  tests  of  specimens  of  Bower-Barffed 
wrought  iron,  submitted  to  tensile  strain,  small  pieces  of  the  oxide 
coating  scaled  off  when  the  strain  reached  28,618  pounds  per  square 
inch,  or  beyond  the  elastic  limit,  and  about  one-half  of  the  ultimate 
strength  of  the  specimen.  In  the  case  of  cast  iron,  the  coating  re- 
mained in  place  uninjured  when  strained  to  the  point  of  rup- 
ture. 

Bower-Barffed  articles  can  be  heated  to  temperatures  approxi- 
mately 400°  Fahr.  and  then  immersed  in  cold  water  without  injury. 
They  resist  the  action  of  sea  air,  sea  water,  sulphurous,  and  other 
gases,  ammonia,  and  all  alkaline  and  organic  acids  in  moderate  solu- 
tion, also  the  caustic  action  of  lime  and  hydraulic  cement  either  dry 
or  damp.  They  are,  however,  affected  by  strong  solutions  of  sul- 
phuric and  hydrochloric  acids. 


BOWER-BARFF  COATINGS. 


169 


A  comparative  test  of  the  resistance  to  corrosion  of  a  number  of 
protective  coatings  under  different  exposures  resulted,  viz. :  * 

CHANGE  IN  WEIGHT  OF  WROUGHT  AND  CAST  IRON  WITH  DIFFERENT  PROTEC- 
TIVE COATINGS  AND  UNDER  DIFFERENT  CONDITIONS,  IN  POUNDS  PER 
SQUARE  FOOT  OF  SURFACE  PER  ANNUM. 

WROUGHT-IRON  SHEETS  (No.  23  GAUGE,  BLACK). 


Protective  Coatings. 

Exposed  to  the  weather 
Inland. 

Immersed  in  — 

Average 
gain. 

Canada. 

New  York 
State. 

Fresh 
water. 

Sewage. 

Bo  wer-Bar  ffed  . 

.0 
gain,  .002.0 
.0 
gain,  .000.4 
"      .001.0 
"      .001.3 
"      .000.2 

gain,  .000.3 
"     .000.1 
.000.5 

gain,  .003.1 
.022.6 
.005.0 

.006.7 
.019.4 
.050.4 
.045.9 
.083.9 
.137.0 
.179.0 

.003.6 
.007.1 
.003.1 
.080.5 
.117.0 
.169.0 
.182.0 

.002.5 
.006.2 
.013.5 
.042.0 
.051.2 
.082.5 
.091.6 

Tinned  
Nickel-plated  .... 

Galvanized.  .  .  . 
Barffed  \.. 
Black  —  i.e.,  unprotected  . 

Copper-plated.  .  . 

Average  gain 

.000.2 

.005.1 

.074.6 

.080.3 

.040 

CAST-IRON  PLATES. 


Protective  Coatings. 

Exposed  to  the  weather 
Inland. 

Immersed  in  — 

Average 
gain. 

Canada. 

New  York 
State. 

Fresh 
water. 

Sewage. 

Bower-Barffed 

gain,  .004.0 
"      .000.6 
.0 

gain,  .003.4 
"      .004.0 
"      .006.3 

gain,  .003.1 
.001.9 
.0 
gain,  .003.1 
.002.5 
"      .005.0 
"      .012.0 

gam,.  005.5 
.000.2 
.049.1 
.065.5 
.131.7 
.150.8 
.148.3 

.001.4 
.008.4 
.061.0 
.061.0 
.083.3 
.119.2 
.272.4 

ga  n,  .002.8 
.002.8 
.027.5 
.041.1 
.053.5 
.067.8 
.106.6 

and  paraffined.  .  . 
Galvanized  

Tinned.                         ... 

Nickel-plated  
Copper-plated  .  .  . 

Black  —  i.e.,  unprotected  
Average  gain  

.002.9 

.002.1 

.007.2 

.086.7 

.041 

The  cost  of  applying  the  process  must  necessarily  vary  with  the 
size,  weight,  and  other  characteristics  of  the  article  to  be  treated. 
For  builders'  hardware  and  that  class  of  articles  called  shelf  goods, 
domestic  articles,  etc.,  the  cost  is  about  5  per  cent  of  the  net  cost  of 
the  goods  to  the  manufacturer.  Wrought-iron  grilling,  office  rail- 
ings, and  the  better  class  of  scroll  and  fancy  work  cost  about  two 
cents  per  pound.  Wrought-iron  steam  and  water-pipe  is  coated  for 
about  the  same  expense  per  pound  as  is  required  to  paint  it.  A 
further  benefit  to  this  class  of  articles  is,  that  the  inside  of  the  pipe 

*  Trade  catalogue.  "Rustless  Iron  and  Steel.  The  Bower-Barff  and 
Wells  Processes."  (Pamphlet  Number  V.  Illustrated.)  By  the  Bower-Barff 
Rustless  Iron  Company,  New  York,  1896. 


170  BOWER-BARFF  COATINGS. 

receives  the  same  coating  as  the  external  parts.  Wrought-iron  I 
beams,  channels,  and  other  shapes  entering  into  building  construc- 
tions can  be  treated  very  cheaply;  the  principal  expense  is  first  cost 
of  the  furnace;  the  actual  operating  expenses  are  very  small — frac- 
tions of  a  cent  per  pound. 

The  Iron  Column  of  Delhi* 

The  iron  column  of  Delhi,  India  (see  Frontispiece),  is  20  feet  high 
above  ground,  16  inches  in  diameter  at  the  base,  and  12  inches  at  the 
top,  with  an  ornate  Persian  capital  3^  feet  hi  height.  The  base  has 
a  Persian  inscription  of  six  lines  on  the  western  side,  symbolizing 
the  deeds  of  the  Rajah  Dhawa,  who  reigned  in  the  ninth  century  B.C. 
Beck,  in  his  "  History  of  Iron,"  places  its  erection  in  the  early  part 
of  the  fourth  century  A.D.,  but  other  authorities  place  it  in  the  ninth 
century  B.C.,  corresponding  to  the  inscription  upon  it. 

Early  excavations  to  the  depth  of  26  feet  did  not  reach  the  bot- 
tom, but  subsequently  it  was  found  to  rest  upon  forged-iron  beams, 
bedded  and  anchored  to  the  stone  foundations.  A  short  distance 
below  the  ground  it  is  2  feet  4  inches  in  diameter,  and  evidently  was 
forged  from  a  large  number  of  wrought-iron  blooms.  Its  estimated 
weight  is  seventeen  tons. 

It  stands  alone  above  all  other  relics,  a  monument  commemora- 
tive of  the  state  of  the  mechanical  arts  in  prehistoric  times,  not  only 
for  its  construction  and  preservation,  but  its  transportation  from 
some  unknown  and  evidently  far-distant  place  of  manufacture  and 
its  erection  in  situ.  This  would  be  considered,  at  the  beginning  of 
the  twentieth  century,  an  exceedingly  creditable  example  of  engi- 
neering skill,  and  it  will  probably  remain  centuries  after  most  of  the 
present-day  ferric  constructions  have  crumbled  to  red  rust. 

It  is  free  from  corrosion,  and  while  this  in  a  measure  may  be  due 
to  the  climate  of  India  not  being  inducive  of  corrosion,  it  cannot  alone 
be  the  reason  of  its  protection,  for  other  iron  articles,  both  large  and 
small,  bear  testimony  to  corrosive  effects  under  the  same  exposure 
and  climate.  A  reason  for  its  non-corrosion  has  been  given:  that  in 
the  earlier  days  following  its  erection  it  was  considered  a  part  of  the 
religious  duty  of  every  pilgrim  to  the  holy  shrine  near  which  it  is 
located  to  climb  it,  and  as  the  pilgrims  annointed  their  bodies  with  oil 
as  a  part  of  their  devotional  exercises,  that  more  or  less  of  this  oil  was 

*  Iron  Age,  August  1,  1895,  p.  215. 


IRON  COLUMN  OF  DELHI.  171 

left  upon  the  column  and  thus  protected  it.  But  for  the  past  two 
hundred  years  or  more,  so  far  as  known,  no  such  greased-pole  gym- 
nastical  devotions  have  been  practised,  and  the  coatings  of  oil,  if  any 
ever  were  thus  applied,  must  have  long  since  been  dissipated,  as 
they  would  doubtless  have  been  palm  or  some  other  vegetable  oil  or 
camel's  fat,  all  of  a  non-siccative  nature. 

The  ornate  capital  is  as  free  from  corrosion  as  the  shaft  of  the 
column,  so  unless  the  pilgrims  climbed  this  as  well  as  the  shaft  (as  a 
sailor-boy  mastheads  his  ship's  truck),  and  possibly  stood  on  their 
heads  as  a  further  sign  of  exalted  zeal,  the  capital  could  not  have 
received  the  oil  treatment  to  protect  it.  The  part  of  the  column 
underground  surely  had  no  such  acrobatic  oleaginous  distribution, 
and  is  comparatively  as  free  from  corrosion  as  the  part  above  ground. 
Every  indication  in  the  appearance  of  the  column  shows  that  after 
it  had  been  forged  and  finished,  the  inscriptions  and  capital  still 
bearing  the  chisel-marks  on  the  ornaments,  it  was  subjected  for  its 
entire  length  to  a  process  identical  to  that  of  the  modern  Bower- 
Barff  process,  which  has  proven  to  be  quite  as  effective  to  prevent 
corrosion  in  this  instance  as  in  any  of  the  modern  examples  of  this 
protective  method. 


CHAPTER  XVII. 

GALVANIZING.        ELECTRO-CHEMICAL    AND    OTHER    ANTI-CORROSIVE 
ZINC  PROCESSES. 

Galvanizing  .* 

GALVANIZING  to  protect  the  surface  of  large  articles,  such  as  enter 
into  the  construction  of  railway  viaducts,  bridges,  roofs,  and  ship- 
work,  has  not  reached  the  point  of  appreciation  that  possibly  the 
near  future  may  award  to  it.  Certain  fallacies  existed  for  a  long  time 
as  to  the  relative  merits  of  the  dry  or  molten  and  the  wet  or  electro- 
lytical  methods  of  galvanizing.  The  latter  was  found  to  be  too 
costly  and  slow,  and  the  results  obtained  were  erratic  and  not  satis- 
factory, and  soon  gave  place  to  the  dry  or  molten-bath  processes  as  in 
practice  at  the  present  day;  but  the  difficulty  of  management  in  con- 
nection with  large  baths  of  molten  material,  the  deterioration  of  the 
bath,  and  other  mechanical  causes  limit  the  process  to  articles  of  com- 
paratively small  size  and  weight. 

The  electro-deposition  of  zinc  has  been  subject  to  many  patents, 
and  the  efforts  to  introduce  it  have  been  lamentable  failures  in  both 
a  mechanical  and  financial  sense.  Most  authorities  recommend  a 
current  density  of  18  or  20  amperes  per  square  foot  of  cathode  sur- 
face, and  aqueous  solutions  of  zinc  sulphate,  acetate  or  chloride, 
ammonia  chloride  or  tartrate,  as  being  the  most  suitable  for  deposition. 

Herman's  process  has  been  experimented  with  on  a  commercial 
scale,  the  chief  feature  being  the  addition  of  the  sulphates  of  the 
alkalies  or  alkali  earth  to  a  weak  solution  of  zinc  phosphate. 

Electrolytes  made  by  adding  caustic  potash  or  soda  to  a  suitable 
zinc  salt  have  been  found  to  be  unworkable  in  practice,  on  account 
of  the  formation  of  an  insoluble  zinc  oxide  on  the  surface  of  the  anode 
and  the  resultant  increased  electrical  resistance;  the  electrolytes  are 

*  Excerpts  from  a  paper  by  the  author,  presented  at  the  New  York  meeting 
(December,  1894)  of  the  American  Society  of  Mechanical  Engineers,  and  form- 
ing part  of  Volume  XVI  of  the  Transactions.  Also  Transactions  of  the  American 
Society  of  Mechanical  Engineers,  Vol.  XV,  1894,  Paper  No.  598,  pp.  998-1073. 

172 


GALVANIZING.  173 

also  constantly  getting  out  of  order,  as  more  metal  is  taken  out  of  the 
solution  than  could  possibly  be  dissolved  from  the  anodes  by  the 
chemicals  set  free,  on  account  of  this  insoluble  scale  or  furring  up  of 
the  anodes,  which  sometimes  reaches  J  inch  in  thickness. 

To  all  intents  and  purposes  the  deposits  obtained  from  acid  solu- 
tions under  favorable  circumstances  are  fairly  adhesive  when  great 
care  has  been  exercised  to  thoroughly  scale  and  clean  the  surface  to  be 
coated,  and  which  is  found  to  be  the  principal  difficulty  in  the  appli- 
cation of  any  electro-chemical  process  for  copper,  lead,  or  tin,  as 
well  as  for  zinc,  and  that  renders  even  the  application  of  paint  or 
other  brush  compounds  so  futile  unless  honestly  complied  with. 
Unfortunately  these  acid  zinc  coatings  are  of  a  transitory  nature, 
their  durability  being  incomparable  with  hot  galvanizing,  as  the 
deposit  is  porous  and  retains  some  of  the  acid  salts,  which  cause 
a  wasting  of  the  zinc  and  consequently  the  rusting  of  the  iron  or 
steel.  Castings  coated  with  acid  zinc,  rust  comparatively  quickly, 
even  when  the  porosity  has  been  reduced  by  oxidation,  aggravated 
no  doubt  by  some  of  the  corroding  agents,  sal-ammoniac,  for  in- 
stance, being  forced  into  the  pores  of  the  metal.  In  wrought  iron, 
the  cinder  is  porous,  and  holds  the  acid,  and  induces  corrosion. 

The  relative  porosity  of  zinc  coating,  applied  by  different  methods, 
is  shown  by  the  following  micrographs,  Figs.  25  and  26,  taken  from 
The  Engineer,  September  28, 1894. 


FIG.  25. — Zinc  coating  applied  by  FIG.  26. — Deposit  from  zinc  sulphate 
hot  galvanizing  process,  magnified  solution  (acid),  magnified  five  diam- 
five  diameters.  eters. 

Other  matters  of  serious  moment  in  the  acid  electro-zincing  proc- 
ess, aside  from  the  slowness  of  operation,  were  the  uncertain  nature, 
thickness,  and  extent  of  the  coating  on  articles  of  irregular  shape, 
and  the  formation  of  loose  dark-colored  patches  on  the  work,  the 


174  GALVANIZING. 

unhealthy  non-metallic  look,  and  want  of  brilliancy  and  lustre  pre- 
vented engineers  and  the  trade  from  accepting  the  process  or  its 
results  except  for  the  commoner  articles  of  use. 

The  Cowper-Coles  process  of  electro-zincing  articles  claims  to 
overcome  all  these  difficulties,  and  plants  are  in  process  of  erection 
with  a  bath  of  some  14,100  gallons  capacity,  capable  of  turning  out 
forty  tons  of  light  work  per  week,  and  in  which  it  is  proposed  to 
treat  the  plates  of  vessels  sixty  feet  in  length  upon  one  or  both  sides, 
and  the  frames  of  such  vessels  as  torpedo-boat  destroyers  and  kin- 
dred craft  after  riveting  up.  These  plates  and  frames  are  given  a 
thin  coating  of  zinc  by  this  process  that  appears  to  be  perfectly  uni- 
form in  character  and  extent  whatever  the  shape  of  the  piece  may  be, 
and  however  numerous  the  lugs,  flanges,  mortises,  or  core-holes.  It 
is  called  "zinc- flashing";  that  is,  coating  the  iron  or  steel  article, 
after  pickling  and  cleaning,  with  a  thin  coat  of  zinc  about  one  ounce 
per  square  foot  of  surface,  which  resists  the  inclemency  of  the  weather 
and  mechanical  injury  as  well  as  a  thicker  coat,  and  is  found  to  afford 
sufficient  protection  in  most  cases,  and  is  adequate  protection  until 
such  time  as  it  is  ready  to  receive  the  usual  paint  coatings. 

To  obviate  any  tendency  of  the  paint  to  peel  from  the  zinc  sur- 
faces, as  it  generally  manifests  a  disposition  to  do,  it  is  recommended 
to  coat  all  the  zinc  surfaces,  previous  to  painting  them,  with  the 
following  compound:  One  part  chloride  of  copper,  one  part  nitrate 
of  copper,  one  part  sal-ammoniac,  dissolved  in  sixty-one  parts  water, 
and  then  add  one  part  commercial  hydrochloric  acid.  When  the  zinc 
is  brushed  over  with  this  mixture,  it  oxidizes  the  surface,  turns  black 
and  dries  in  from  twelve  to  twenty-four  hours,  and  may  then  be 
painted  over  without  danger  of  peeling.  Another  and  more  quickly 
applied  coating  consists  of  bichloride  of  platinum,  one  part  dissolved 
in  ten  parts  distilled  water  and  applied  either  by  a  brush  or  sponge. 
It  oxidizes  at  once,  turns  black,  and  resists  the  weak  acids,  rain, 
and  the  elements  generally. 

There  are  plso  a  number  of  trade-mark,  or  proprietary,  mixtures  to 
prevent  the  peeling  of  paint  applied  to  zinc.  "  Uniter,"  an  English  com- 
pound, and  "Galvanum,"  an  American  paint  in  light-brown  and  dark- 
gray  colors,  are  favorably  recommended.  Carbon  and  asphaltum 
paint,  containing  a  large  percentage  of  bisulphide  of  carbon  in  the 
vehicle,  also  adheres  well  to  galvanized  iron.  Its  nauseating  odor 
and  highly  inflammable  character  during  its  application  are  strong 
points  against  its  use. 


GALVANIZING.  175 

Galvanized-iron  sheets  that  are  corrugated  after  galvanizing 
corrode  more  rapidly  than  uncorrugated  sheets.  Sharp  angles  and 
twists  in  the  sheet  also  corrode  quickly.  The  thin  zinc-coating  atoms 
are  brittle  naturally,  and  are  opened  to  allow  moisture  to  reach  the 
metal  they  cover.  This  being  a  more  elastic  metal,  plates  coated  with 
it  do  not  show  the  bending  effects  so"  strongly,  yet  they  are  apparent. 

Double-coated  tin,  zinc,  or  terne  plates  are  from  two  to  three  times 
more  resistant  to  corrosion  than  single-coated  plates.  The  second 
coating,  like  the  second  coat  of  paint  on  a  painted  surface,  fills 
the  shrinkage,  cracks,  and  pores  in  the  first  coat.  Galvanized-iron 
pipes  used  for  gas  and  water  service  in  the  ground  have  only  a  life 
of  12  to  15  years,  the  outside  coating  of  zinc  being  destroyed  by  gal- 
vanic action  induced  by  the  acid  elements  in  the  soil.  If  the  soil 
contains  furnace  cinders,  the  corrosion  is  hastened.  The  screwed 
ends  and  other  parts  of  the  pipe  where  the  galvanizing  has  been  cut 
away  are  the  parts  first  corroded.  In  general  all  galvanized  pipe- 
work is  so  poorly  cleaned  from  mill-scale  and  grease  prior  to  galvan- 
izing, that  the  pipes  are  less  enduring  than  with  a  common  coal-tar 
pitch  dip  coating. 

Zinc  surfaces,  after  a  brief  exposure  to  the  air,  become  coated 
with  a  thin  film  of  oxide — insoluble  in  water,  which  adheres  tena- 
ciously, forming  a  protective  coating  to  the  underlying  zinc.  So  long 
as  the  zinc  surface  remains  intact,  the  underlying  metal  is  protected 
from  corrosive  action,  but  a  mechanical  or  other  injury  to  the  zinc 
coating,  that  exposes  the  metal  beneath  to  the  presence  of  moisture, 
causes  a  very  rapid  corrosion  to  be  inaugurated,  the  galvanic  action 
being  changed  from  zinc  positive  to  zinc  negative,  and  the  iron  as 
the  positive  element  in  the  circuit  is  corroded  instead  of  the  zinc. 

When  galvanized  iron  is  immersed  in  a  corrosive  liquid,  the  zinc 
is  attacked  in  preference  to  the  iron,  provided  both  the  exposed  parts 
of  the  iron  and  the  protected  parts  are  immersed  in  the  liquid.  The 
zinc  has  not  the  same  protective  quality  when  the  liquid  is  sprinkled 
over  the  surface  and  remains  in  isolated  drops.  Sea  air  being  charged 
with  saline  matter  is  very  destructive  to  galvanized  surfaces,  form- 
ing a  soluble  chloride  by  its  action.  As  zinc  is  one  of  the  metals  most 
readily  attacked  by  acids,  ordinary  galvanized  iron  is  not  suitable 
for  positions  where  it  is  to  be  much  exposed  to  an  atmosphere  charged 
with  acids  sent  into  the  air  by  some  manufactories,  or  to  the  sulphuric- 
acid  fumes  found  in  the  products  of  combustion  of  rolling-mills,  iron, 
glass,  and  gas  works,  etc.;  and  yet  we  see  engineers  of  note  covering 


176 


GALVANIZING. 


in  important  buildings  with  corrugated  galvanized  iron  and  using 
galvanized-iron  tie-rods,  angles,  and  other  construction  shapes,  in 
blind  confidence  of  the  protective  power  of  the  zinc  coating;  else  in 
supreme  indifference  as  to  the  future  consequences  and  catastrophes 
that  may  arise  from  their  failure. 


•So 

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NOT.ES.J 

Dissolve  1  in  "Water. 
Add  excess  of  2.   Exact 
proportions  not  stated. 
Current  Density  about 
20  Amperes-]**  &),R5 
Precipitate  4  fcotn^ui- 
phate  by  Eotash. 
(FOB  Cast  Iron)  Ecopor- 
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(Hies  not  stated. 

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Ad(L«)  and  9  injest  of 

water.    Mil  well. 

Dissolve  T8  in  Water. 
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Sirm  deposit'wlth 
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FIG.  27. — Zincing  solutions  recommended  by  various  authorities. 

The  comparative  inertia  of  lead  to  the  chemical  action  of  many 
acids  has  led  to  the  contention  that  it  should  form  as  good  if  not  a 
better  protection  to  iron  than  zinc,  but  in  practice  it  is  found  to  be 
deficient  as  a  protective  coating  against  corrosion.  A  piece  of  lead- 
coated  iron  or  terne  plate  placed  in  water  will  show  decided  evi- 
dences of  corrosion  in  twenty-four  hours.  This  is  to  be  attributed 
to  the  porous  nature  of  the  coating,  whether  it  is  applied  by  the  hot 
or  wet  (acid)  process.  The  lead  does  not  bond  to  the  plate  as  well 
as  either  of  the  other  metals,  zinc,  tin,  copper,  or  any  alloys  of  them. 
Lead-coated  iron  corrodes  rapidly  when  exposed  to  the  gases  of  com- 
bustion. The  usual  weight  of  lead-coated  terne-plates  is  about 
f  ounce  to  a  square  foot,  while  hot-process  zinc  coatings  weigh  from 
IY  ounces  minimum  to  3  ounces  maximum,  depending  upon  the 
temperature  of  the  bath,  and  the  slowness  of  removal  therefrom 
giving  time  for  the  article  to  drain  off.  The  following  table  gives 
the  increase  in  weight  of  different  articles  due  to  hot  galvanizing : 


GALVANIZING. 


177 


Description  of  Article. 

Weight  of  Zinc  per 
Square  Foot. 

Percentage  of 
Increase  of 
Weight. 

Thin  sheet  iron  =  .026  inch  No.  22  B.  W.  G.  .  .  . 

•rz-inch  plates 

1  .  196  oz. 
1  76     " 

18.2 
2  0 

4-inch  cut  nails               .        .        

2  19     " 

6  72 

|-inch-dia  bolt  and  nut  

j  approximately 

1  00 

\     1.206oz. 

Tin  is  often  added  to  the  hot  bath  for  the  purpose  of  obtaining  a 
smoother  surface  and  larger  spangles  or  facets, .  but  it  is  found  to 
shorten  the  life  of  the  coating  considerably. 

A  portion  of  a  zinc  coating  applied  by  the  hot  process  was  found 
to  be  very  brittle,  breaking  when  attempts  were  made  to  bend  it; 
the  average  thickness  of  the  coating  was  .015  of  an  inch. 

An  analysis  gave  the  following  result: 

Tin 2.20 

Iron 3.78 

Arsenic trace 

Zinc  (by  difference) 94.02 

A  small  quantity  of  iron  is  dissolved  from  all  the  articles  placed 
in  the  molten-zinc  bath,  and  a  dross  is  formed  amounting  in  many 
cases  to  25  per  cent  of  the  whole  amount  of  zinc  used.  This  zinc-iron 
alloy  is  very  brittle  and  contains  by  analysis  6  per  cent  of  iron,  and 
is  used  to  cast  small  art  ornaments  from. 

Nickel  coatings  produced  galvanically  will  not  protect  iron  from 
corrosion  unless  .02  inch  thick. 

A  hot  galvanizing  plant  having  a  bath  capacity  of  10  feet  by 
4  feet  by  4  feet  6  inches  outside  dimensions,  and  about  1  inch  in 
thickness,  will  cost  $625,  and  will  hold  twenty-eight  long  tons  of  zinc, 
which  at  four  cents  per  pound  will  require  $2500  to  fill  it;  the  heat- 
ing of  this  mass  of  metal  and  its  ever-changing  cold  immersions, 
with  the  waste  by  dross  and  extra  thickness  in  spots,  is  a  constant 
source  of  annoyance  and  expense. 

The  cost  of  an  electro-chemical  or  wet-bath  Cowper-Coles  plant 
of  6700  gallons  bath,  size  30  feet  by  6  feet  by  7  feet,  will  be  but 
slightly  more  than  the  hot  bath  given.  There  is  no  dross  formed 
by  the  use  of  the  Cowper-Coles  process,  and  the  zinc  coating 
formed  is  said  to  resist  the  corroding  action  of  a  saturated  solution 
of  copper  sulphate.  The  English  Post-office  test  for  telegraph  wire 


178 


GALVANIZING. 


coated  by  the  Cowper-Coles  process  shows  much  better  than  hot 
galvanized-iron  wire,  as  per  following  table: 

RESULT  OF  PROCESS   TEST  MADE  ON   SAMPLES  OF  CHARCOAL-IRON  WIRE 
COATED  WITH  ZINC  BY  VARIOUS  PROCESSES. 


Process  Used  to  Coat  the  Wire. 

Grains  of  Zinc 
Per  Square 
Foot. 

Ounces  Per 
Square  Foot. 

Number  of  One- 
minute  Dips; 
Samples  Stood 
without  Showing 
Metallic  Copper. 

Hot  galvanized  

648.5 

1.48 

3 

Acid  bath,  ZnSO4.   .  .  .  

446.4 

1.02 

4 

Cowper-Coles  process 

552  64 

1  26 

5 

A  Cowper-Coles  process  bath  of  a  capacity  of  about  4000  gal- 
lons will  treat  ship-plates  18  feet  long,  and  will  require  an  electrical 
energy  of  2000  amperes  of  5-volt  electro-motive  force. 

With  equal  amounts  of  zinc  per  unit  of  area,  the  zinc  coating  put 
on  by  the  cold  process  is  more  resistant  to  the  corroding  action  of  a 
saturated  solution  of  copper  sulphate  than  is  the  case  with  steel 
coated  by  the  ordinary  hot  galvanizing  process ;  or,  to  put  it  in  another 
form,  articles  coated  by  the  cold  process  should  have  an  equally  long 
life  under  the  same  conditions  of  exposure  that  hot  galvanized  articles 
are  exposed  to,  and  with  less  zinc  than  would  be  necessary  in  the 
ordinary  hot  process. 

The  hardness  of  a  zinc  surface  is  a  matter  of  some  importance. 
With  this  object  in  view,  aluminium  has  been  added  from  a  separate 
crucible  to  the  molten  zinc  at  the  moment  of  dipping  the  article  to  be 
zinced,  so  as  to  form  a  compound  surface  of  zinco-aluminum,  and  to 
reduce  the  waste  formed  from  the  protective  coverings  of  sal-ammo- 
niac, fat,  glycerine,  etc.  The  addition  of  the  aluminum  also  reduces 
the  thickness  of  the  coating  applied. 

Cold  and  hot  galvanized  plates  appear  to  stand  abrasion  equally 
well.  The  thickness  of  the  coating  being  the  same,  tests  by  means 
of  the  Schlerometer  show:  cold  galvanized  sheet,  6;  hot  galvanized 
sheet,  6;  terne-plate,  2;  tin-plate,  2.  The  figures  represent  the  load 
in  grammes  upon  a  diamond  point,  just  sufficient  to  cause  it  to  scratch 
the  specimen. 

The  attempts  to  electro-zinc  iron  and  steel  wire  for  wire  standing 
rigging,  bridge,  or  other  cables  have  not  been  successful;  it  has  not 
been  found  practical  to  produce  a  wire  capable  of  withstanding  more 
than  one  immersion  in  a  copper-sulphate  solution. 


GALVANIZING. 


179 


Both  pickling  and  hot  galvanizing  reduce  the  strength,  distort 
and  render  brittle  iron  and  steel  wires  of  small  sections.  Zinc  fuses 
at  775°  F.  and  vaporizes  at  830°  F.  Hence  the  necessity  of  the  sal- 
ammoniac  bath  that  covers  the  molten  zinc,  prevents  volatilization 
and  acts  as  a  flux  to  unite  the  zinc  and  iron.  The  bath  is  usually 
kept  at  about  1000°  F.  Steel  wire  of  high  breaking  strain  has  its 

TABLE  GIVING  THICKNESS  OF  ZINC  REQUIRED  TO  WITHSTAND  VARYING 
BER  OF  IMMERSIONS  IN  A  SOLUTION  OF  COPPER  SULPHATE. 


WEIGHT  OF  ZINC  PER  SQUARE  FOOT  IN  OUNCES  AV. 

—  2:032 

/ 

/ 

1.974 
—  1T316 

QR7 

/ 

>•      'J 

O 

pe 

\- 

/ 

< 

a: 
<S 

z 

/ 

.000 
(KM 

/ 

/ 

5          i 

I             3             4            .5             6             7             8 

No.  of  1  minute  immersions  in  saturated  solution  of  copper  sulphate 

FIG.  28. 

hardness,  and  consequently  its  ultimate  tensile  strength  and  elonga- 
tional  efficiency,  reduced  by  drawing  the  temper  and  the  formation 
of  an  iron  zinc  alloy  on  the  surface  of  the  wire  by  as  much  as  from 
5  to  10  per  cent.  It  is  the  practice  when  coating  steel  wire  to  keep 
the  bath  at  as  low  heat  as  possible  and  to  run  the  wire  through  it 
at  a  high  rate  of  speed.  Both  these  operations  lead  to  a  waste  of 
zinc  by  reason  of  the  rapid  solidification  of  the  metal  on  the  com- 
paratively cold  wire,  and  consequently  the  ready  breaking  or  crack- 
ing of  the  covering  metal  on  bending  or  twisting  it,  owing  to  the 
difficulty  with  which  molten  zinc  adheres  to  the  steel  except  after 
long  contact  in  the  bath.  In  some  cases  the  wire  is  wiped  between 
asbestos  rubbers  as  it  leaves  the  bath,  but  wire  thus  treated  is  found 
to  resist  corrosion  but  a  very  short  time. 


180  GALVANIZING  AND  GALVANIC  ACTIONS. 

English  manufacturers  have  ceased  galvanizing  their  high-grade 
steel  wire  that  costs  some  $175  per  ton,  on  account  of  the  great  risk 
of  rendering  it  worthless. 

The  Cowper-Coles  or  cold-galvanizing  process  is  used  for  the 
purpose  of  zincing  the  skin  plates  and  frames  of  the  torpedo-boats 
and  torpedo-boat  destroyers  built  for  the  English  navy.  A  plan 
and  elevation  of  this  plant  is  given  in  The  Engineer,  Feb.  28,  1894. 

The  industrial  importance  of  the  successful  application  of  this 
cold-galvanizing  process  can  hardly  be  overestimated,  even  if  its 
application  is  only  to  the  marine  constructions  of  the  future,  and 
it  is  found  to  be  in  any  degree  inapplicable  to  our  present  structures 
and  vessels  in  use.  The  permanency,  continuity,  strength,  and  den- 
sity of  the  coating  given  by  this  process  is  in  all  respects  equal  to 
that  of  hot  galvanizing,  and  the  thickness  of  it  can  be  made  superior 
to  that  given  by  the  hot.  Considering  the  success  that  has  attended 
the  use  of  zinc  to  prevent  corrosion  in  marine  boilers,  where  concen- 
trated hot  saline  fluids  are  the  excitant  medium,  aided  by  the  elec- 
trical conditions  attendant  upon  the  combustion  of  large  quantities 
of  fuel,  it  may  not  be  considered  a  wild  prophecy  to  expect  that  with 
all  of  the  internal  metallic  parts  of  a  steam  vessel  protected  by  an 
application  of  zinc  plates  secured  to  the  framework  of  the  structure 
similar  to  the  application  of  zinc  to  marine  boilers,  that  these  plates 
may  receive  the  energy  of  corrosion,  and  if  not  neutralizing  it  entirely, 
at  least  pass  it  along  in  the  form  of  a  deposit  to  convenient  pockets, 
where  it  could  be  removed,  the  same  as  is  now  done  with  the  wash- 
ings and  dirt  from  the  fire-room  bunkers  and  ballast-chambers. 

This  internal  electro-chemical  process  of  protection  does  not 
appear  so  chimerical  as  at  first  one  might  suppose.  Dr.  Henry  Wurtz  * 
has  proposed  the  protection  of  mining  plants  subject  to  the  intensi- 
fied corrosion  due  to  the  decomposition  of  pyrites  and  other  minerals 
hi  the  mine  waters,  by  connecting  all  of  the  metal  portions  of  the 
mine  as  the  negative  elements  with  a  dynamo  of  sufficient  force  to 
overcome  the  strength  of  galvanic  energy  due  to  the  surfaces  exposed 
being  excited  by  the  corrosive  liquids  in  the  mine,  the  positive  ter- 
minal to  be  connected  to  a  mass  of  hard  coke  in  the  mine  sump. 
These  conditions  vary  but  slightly  from  those  existing  in  the  ship,  and 
it  is  not  improbable  that  experiment  will  determine  that  both  these 
systems  could  be  made  to  work  successfully. 

*  Engineering  Magazine,  May,  1894,  Vol.  VII,  No.  3,  page  297,  "Preservation 
of  Metals  from  Corrosion  by  Electric  Polarization." 


ELECTRO-CHEMICAL  AND  GALVANIC  ACTIONS.  181 

Thermo-electric  currents  arise  from  changes  of  temperatures  in 
all  bodies,  and  set  up  voltaic  action  in  all  cavities,  fissures,  seams, 
and  contact  surfaces  in  the  metal,  which,  though  slight  and  not 
easily  detected,  will  in  time  enlarge  and  waste  them  away  sufficiently 
to  sap  the  strength  of  the  mass. 

Metallic  salts  and  acids  in  mine  waters  intensify  the  corrosion  of 
all  metals  exposed  to  their  action.  The  metal  work  of  railway  tunnels 
is  also  disastrously  affected  by  the  condensed  vapors  of  sulphur, 
carbonic  acid,  and  the  ever-present  moisture  due  to  such  locations. 
The  corrosion  of  the  metals  decreases  the  resistance  of  the  water  to 
voltaic  circuits,  this  corrosion  by  liquids  being  voltaic  phenomena  in 
all  cases.  In  many  cases  it  is  intensified  by  the  moisture  being  in 
the  form  of  drops  instead  of  being  uniformly  spread  over  the  whole 
surface. 

Acids  and  acid  salts  which  are  capable  of  taking  up  iron  oxides 
into  solution  still  further  enhance  the  destruction  by  removing  such 
oxides  and  exposing  the  surfaces  of  the  metal  to  a  fresh  attack  of 
the  corrosive  element.  The  saline  matter  in  solution  that  excites 
voltaic  action  need  not  be  acid.  Any  neutral  salt  which  decreases 
the  resistance  of  the  water  will  qualify  it  to  act  as  the  necessary  liquid 
medium  of  a  voltaic  circuit.  Sea-salt  is  the  commonest  of  all  such 
neutral  salts,  together  with  the  other  chlorides  and  sulphates  of  sea- 
water.  It  enables  corroding  voltaic  action  to  be  set  up  on  all  ferric 
bodies  immersed  therein  or  in  the  air  impregnated  with  their  substance. 

The  Journal  of  the  Society  of  Chemical  Industry,  London,  February 
28,  1894,  details  some  experiments  with  the  galvanic  action  of  sea- 
water  upon  iron  and  steel  structures  in  various  relations  with  each 
other,  such  as  the  constructive  parts  of  trusses,  boilers,  etc.,  to  pre- 
vent the  corrosion  for  which  the  use  of  zinc  and  other  easily  oxidized 
metals  and  alloys  are  suggested,  and  to  be  so  placed  and  connected 
to  the  structure  that  they  will  form  the  electro-positive  element  of 
the  ever-present  galvanic  circuit,  and  by  their  decomposition  protect 
the  structure. 

Mr.  D.  Phillips,  in  a  paper  read  before  the  Institute  of  Civil  Engi- 
neers, in  1885,  cited  the  result  of  an  experiment,  where  "surfaces  of 
bright  pieces  of  plate  iron,  immersed  in  cold  sea- water  for  over  ten 
years  have  been  thoroughly  protected  from  corrosion  by  the  aid  of 
pieces  of  metallic  zinc  in  metallic  contact  with  the  iron ;  while  a  simi- 
lar piece  of  iron  similarly  fitted  and  immersed,  but  having  a  piece 
of  paper  placed  between  the  iron  and  zinc  plate,  received  no  protection 


182  ELECTRO-CHEMICAL  AND  GALVANIC  ACTIONS. 

whatever.  The  water  was  changed  twice  annually,  and  the  oxide 
removed  from  the  zinc  by  filing.  Under  these  circumstances  the  iron 
became  gradually  coated  with  a  film  of  leaden-colored  deposit  when 
wet,  but  hard  and  white  when  dry.  The  effect  in  other  respects  was 
that,  on  every  occasion  that  the  oxide  was  removed  from  the  zinc  and 
the  deposit  from  the  iron  specimens,  on  being  returned  to  the  water 
small  globules  formed  on  the  zinc,  and  on  reaching  j\  inch  in  diam- 
eter released  themselves  and  flew  to  the  surface." 

The  proportions  necessary  to  insure  complete  protection  from 
corrosion  in  marine  boilers  are  one  square  foot  of  zinc  to  fifty  square 
feet  of  heating  surface  in  new  boilers,  which  may  be  diminished  after 
a  time  to  one  in  seventy-five  or  even  one  in  one  hundred  square  feet. 
Merely  placing  the  zinc  in  trays,  hangers,  or  strips  will  not  insure 
metallic  contact.  The  better  and  generally  recognized  method  of 
fixing  the  zinc  is  to  place  a  number  of  studs  in  the  sides  of  the  furnaces 
and  combustion-chambers,  and  to  bolt  on  to  these  studs  the  zinc 
plates,  which  should  be  about  10"X6"Xl''.  It  is  important  to  see 
that  the  contact  surfaces  are  clean  and  bright,  and  the  nut  screwed 
close  down  to  the  zinc  to  exclude  the  water  and  deposits  from  the 
contact  surfaces,  thus  comparatively  insulating  them  and  preventing 
the  galvanic  action.  Otherwise  the  zinc  is  acted  upon  mostly  as  a 
solvent  that  renders  the  water  innocuous  or  non-exciting,  but  does 
not  prevent  the  water  from  forming  a  hard  scale  when  it  is  saturated. 

Sheet  zinc  has  proven  to  be  a  durable  roofing  material.  Zinc 
is  reduced  in  density  from  6.86  to  7.2  in  the  process  of  rolling  into 
sheets,  which  closes  the  pores  and  renders  the  metal  less  affected 
than  tin-plate  from  the  ammonia,  carbonic  acid  and  atmospheric 
gases. 

Berlin  zinc  roofing-plates  (unpainted)  have  been  found  to  be  not 
materially  affected  after  many  years'  exposure.  The  weather  formed 
a  thin  film  of  oxide  on  their  surfaces  that  effectually  prevented  further 
oxidation.  A  few  cases  reported  are  as  follows. 

The  Cloisters  of  Canterbury  were  covered  with  zinc  roofing  and 
were  uninjured  after  33  years. 

The  Portsmouth  Dock  Yard  Buildings'  roofs  were  uninjured  after 
24  years.  The  Great  Western  Railway  Station  roof  at  Rugby  was 
uninjured  after  20  years.  Other  railway-station  roofs  were  uninjured 
after  15  to  20  years.  The  zinc  roofing  required  painting  if  sulphurous 
acid  was  in  the  atmosphere. 

Tin  roofing  corrodes  from  the  inside  of  the  coating.     It  is   also 


TIN,  ZINC,  AND   LEAD  ALLOYS.  183 

porous,  quite  as  much  so  as  a  single  coat  of  paint.  The  tin-plate  as 
it  leaves  the  molten  dipping-bath  becomes  covered  with  a  thin  film 
of  fluxing  or  non-drying  oil  that  fills  the  pores  of  the  tin,  and  if  the 
roofing  is  painted  soon  as  laid,  this  film  prevents  the  paint  from 
adhering  to  the  tin,  just  as  a  machine  grease  prevents  a  paint  from 
bonding  to  a  surface.  A  few  months'  exposure  to  the  atmosphere 
slightly  oxidizes  the  tin,  and  this  oxide  absorbs  the  oily  coating  and 
allows  the  weather  to  wash  it  away  and  the  paint  has  a  clean 
metallic  surface  to  bond  to.  Tin-plates  doubly  dipped  are  less  por- 
ous and  more  durable. 

The  quality  of  commercial  tin-plate  is  greatly  inferior  to  that  made 
forty  years  ago,  and  appears  to  retrograde  yearly.  Lead,  antimony, 
and  other  metals  are  mixed  with  the  tin  in  the  dipping-bath,  and 
greatly  reduce  its  resistance  to  corrosion.  None  of  the  adulterants 
form  a  true  alloy;  they  are  only  mechanical  mixtures.  They  all 
differ  in  oxidizing  power  and  electrical  affinities.  The  lead  is  electro- 
negative to  the  tin  and  zinc,  which  again  are  of  opposite  electrical 
natures. 

The  amount  of  sulphurous  and  carbonic  acids  and  ammonia  in  the 
atmosphere  is  enough  to  form  the  excitant  element  needed  to  decom- 
pose them  one  after  another,  until  the  coating  is  made  porous 
and  the  iron  is  corroded  in  turn.  The  life  of  the  tin-plates  is  also 
governed  in  a  great  measure  by  the  want  of  care  that  they  should 
receive  in  the  preliminary  pickling  with  muriatic  acid,  to  free  them 
from  the  mill-scale  that  always  attends  their  rolling.  Ordinary 
washing  with  lime-water  does  not  remove  the  whole  of  this  acid,  and 
the  tin  coating  usually  has  a  double  galvanic  pile  in  a  sandwich  form, 
ready  for  duty  on  the  least  encouragement. 

There  are  brands  of  tin-plate  as  honestly  coated  at  the  present 
day,  and  as  reliable  in  all  respects,  as  any  ever  made,  but  they  are 
an  exception,  not  the  rule.  Price  and  the  gullibility  of  the  purchaser 
govern,  as  in  many  other  modern  industries.  (See  Fig.  6,  page  38.) 

Red-lead  paint  coatings  soften  tin  roofing,  but  do  not  wholly 
destroy  it,  although  some  of  the  tin  may  be  changed  to  a  white  oxide 
that  is  easily  removed  by  atmospheric  influences. 


CHAPTER  XVIII. 

INERT   PIGMENTS,    OR   ADULTERANTS. 

THE  different  substances  known  as  inert  pigments  are  used  to  a 
great  extent  in  the  preparation  of  nearly  all  mixed  paints,  particularly 
in  the  house  paints,  where  the  amount  of  one  or  more  of  them  fre- 
quently exceeds  that  of  the  base  pigment. 

However  admissible  their  use  (on  account  of  cost  only)  may  be  in 
paints  not  classed  as  protective  ferric  coatings,  their  durability  in 
any  case  is  determined  by  the  character  of  the  weakest  element  in 
the  associated  group  to  resist  atmospheric  conditions,  whatever  the 
base  pigment  may  be. 

The  manufacture  of  "patent  pants"  would  be  almost  nil  were  it 
not  for  the  very  liberal  use  of  these  inert  pigments.  They  are  said 
to  correct  almost  every  detrimental  quality  in  the  basic  pigments. 
Yet  with  all  of  their  boasted  virtues,  there  is  hardly  a  manufacturer 
of  paint  willing  to  admit  their  use,  or  that  will  furnish  an  analysis  of 
his  product  that  contains  them. 

Many  of  the  uses  and  characteristics  of  these  inerts,  fortifiers, 
or  adulterants  have  been  mentioned  in  the  basic  pigments  chapters 
and  elsewhere  in  this  work,  but  are  brought  together  here  for  com- 
parison and  ready  reference. 

Carbonate  of  lime  (CaCo)  in  some  form  other  than  as  quick- 
lime (calcined  limestone  or  marble)  is  often  used  as  a  desirable  adul- 
terant of  many  paints.  It  is  claimed  to  be  specially  favorable  to 
correct  the  sulphur  element  present  in  iron  oxides. 

Chalk  is  a  friable  carbonate  of  lime  that,  on  account  of  its  cheap- 
ness and  several  colors,  is  the  most  used.  Its  specific  gravity  is  2.2 
to  2.8.  According  to  the  basic  oxides  in  it,  the  colors  are  white,  red. 
gray,  and  black.  It  contains  about  2  per  cent  of  clay  besides  free 
silica,  magnesia,  and  chloride  of  calcium,  and  carries  a  large  quantity 
of  water.  The  latter  is  loosely  held,  and  as  calcination  of  chalk  is 
not  thought  necessary  when  used  for  an  adulterant,  the  moisture 
is  carried  into  the  paint  to  its  detriment. 

184 


INERT  PIGMENTS,   OR  ADULTERANTS.     WHITING.         185 

Whiting.  Spanish  white  and  other  trade-name  whites  are  prepa- 
rations from  chalk.  When  used  to  correct  the  sulphur  element  in 
iron-oxide  paints,  10  per  cent  by  weight  of  the  pigment  is  often  added. 
It  is  as  easily  dissolved  by  moisture  as  whitewash.  Its  use  for  the 
adulteration  of  white-lead  pastes  or  paints  is  common  rather  than 
exceptional,  and  frequently  composes  50  per  cent  of  the  paint. 
Whiting,  when  used  as  a  pigment,  is  liable  to  form  a  chemical 
reaction  between  the  oil  and  itself  that  results  in  the  formation  of  a 
lime  soap,  which  is  not  at  all  a  durable  substance. 

Putty,  however  (a  mixture  of  whiting  and  oil),  is  a  very  durable 
body,  and  withstands  atmospheric  exposure  and  water  remarkably 
well.  In  this  form  it  illustrates  the  theory  that  the  pigment  is  the 
life  of  the  paint.  The  small  amount  of  oil  in  the  composition  of  putty 
is  the  cause  of  its  quick  drying.  Its  mass,  when  applied,  greatly 
exceeds  that  of  a  paint  coating,  and  its  shrinkage  solidifies,  instead 
of  rupturing  it,  by  a  movement  in  a  number  of  directions,  as  in  a 
paint. 

Barytes  (Heavy  Spar),  Ba.SO4.  Specific  gravity,  4.3  to  4.7.  The 
natural  sulphate  of  barium,  consisting  of  one  atom  of  barium  oxide 
(BaO)  =  65.67  per  cent,  and  one  atom  of  sulphuric  acid,  34.33  per 
cent.  It  is  the  heaviest  of  all  minerals,  and  is  found  in  all  stages  of 
purity,  in  transparent,  colorless,  white  to  yellow  crystals,  also  in  a 
granular  and  compact  form  in  heavy  beds  resembling  marble.  It 
is  common  in  all  metallic  veins,  allied  with,  or  changed  to,  calc- 
spar,  spathic  iron  ore,  cerussite,  quartz,  limonite,  pyrites,  and  other 
substances.  It  is  the  white  variety  that  is  ground  for  a  pigment, 
but  lacks  the  opacity  or  light-reflecting  or  coloring  power  to  form  of 
itself  a  good  pigment.  It  grinds  hard,  splintery,  and  irregular,  and 
is  used  to  give  weight  to  paper- stock,  zinc  oxide,  gypsum,  and  all  the 
other  light  pigments  that  lack  weight  to  enable  them  to  masquerade 
as  white  lead.  (See  Chapter  VI.) 

Barytes  brightens  light-colored  paints,  though  of  poor  coloring 
or  light-dispersing  power;  also  spreads  easily  and  saves  oil.  It  is 
mixed  with  nearly  all  pigments,  and  by  the  use  of  a  stiff  or  short 
bristle  brush,  covers  a  large  surface  with  a  resemblance  of  a  good 
paint. 

White  lead  does  not  cover  so  well  with  barytes,  but  zinc  oxide 
covers  better.  Zinc  oxide  lacks  weight  that  barytes  furnishes  and 
also  saves  oil,  advantages  not  ignored  by  the  cheap  paint-com- 
pounders.  Barytes  does  not  unite  with  the  oil  in  any  degree.  From 


186         INERT  PIGMENTS,   OR   ADULTERANTS.     BARYTES 

its  weight  and  non-bonding  nature,  the  paint  is  inclined  to  run  on 
vertical  surfaces.  This  tendency  requires  the  use  of  large  amounts 
of  volatiles  or  quick  driers.  Barytes  alone  is  the  poorest  of  pigments. 

Floated  barytes  is  the  ground  natural  sulphate  of  baryta  floated 
off  in  water  to  give  a  finer  product. 

Artificial  barytes  (Blanc-Fixes)  is  made  by  heating  barium  car- 
bonate with  sulphuric  acid  and  precipitating  the  artificial  barytes 
from  the  solution.  It  is  less  crystalline  than  the  natural  sulphate 
and  has  a  greater  covering  power. 

Baryta  white,  permanent  white,  constant  white,  etc.,  are  of 
this  class  of  pigments.  Blanc-Fixe  mixed  with  the  mineral  barytes 
compose  the  principal  substances  in  most  of  the  commercial  white 
patent  paints. 

Lithopone,  a  trade-mark  for  one  of  these  mixtures,  has  an  extended 
sale  under  the  guise  of  white  lead.  Trade-marks  are  easily  invented, 
but  they  add  no  durability  to  the  paint.  They  move  around  in  paint 
literature  as  easily  as  some  of  the  substances  covered  by  the  name 
move  in  the  vehicle  that  gives  them  a  home,  if  not  rest. 

Barytes  as  a  pigment,  exposed  to  air  or  on  underground  bodies, 
condenses  water  and  carbonic  acid  and  is  converted  into  a  carbonate 
with  the  evolution  of  sulphuretted  hydrogen.  This  decomposing 
feature  in  barytes  seems  to  be  ignored  by  paint-compounders,  but 
to  it  the  failure  of  many  coatings  can  be  attributed. 

Rose's  experiments  show  that  barytes  in  any  form,  when  acted 
upon  by  water,  evolves  sulphuretted  hydrogen  and  sulphurous  acid, 
leaving  the  decomposed  lime  free. 

Hansfeld  has  also  shown  that  sulphate  of  lime  is  decomposed  by 
the  galvanic  action  of  two  metals  or  metallic  oxides  in  contact  under 
the  ordinary  exposures  of  a  paint.  When  both  barytes  and  gypsum 
are  present  in  a  paint,  this  galvanic  action  between  three  substances 
is  certain  to  occur.  Mixtures  of  barytes  and  gypsum  with  the  oxides 
or  carbonates  of  zinc  or  lead  will  in  no  degree  protect  any  one  of 
them.  They  decompose  one  after  the  other;  the  first  to  break  down 
only  adds  to  the  electrolytic  energy  to  hurry  up  the  decomposition 
of  the  others.  The  thin  film  of  oil  in  which  the  pigments  are  embedded 
is  sufficiently  porous  to  admit  the  atmospheric  moisture  and  carbonic 
acid  necessary  to  start  up  the  disintegrating  process. 

Putty  made  from  barytes,  whiting,  and  oil  dries  into  a  hard, 
brittle  mass  that  crumbles  easily.  Glycerine  added  to  it  only  tem- 
porarily defers  the  extreme  shrinkage  and  crumbling. 


INERT  PIGMENTS,   OR  ADULTERANTS.     BRICK-DUST.       187 

Probably  the  greater  number  of  the  mixed  white-lead  pastes  and 
paints  sold  in  the  world  contain  barytes;  as  it  costs  only  $10  to  $20 
per  ton,  or  about  one-sixth  as  much  as  white  lead  or  zinc  oxide,  the 
temptation  to  use  it  in  place  of  these  pigments  is  not  always  resisted. 
As  a  rule  no  responsible  paint  firm  with  a  business  reputation  to 
sustain  will  sell  a  barytes  adulterated  paint  under  their  name. 

Additional  data  about  the  presence  of  barytes  in  a  paint  is  given 
in  Chapter  XXIX.  The  covering  and  coloring  power  of  barytes  in 
comparison  with  white  lead  and  zinc  oxide  are  shown  by  Fig.  29. 


FIG.  29. — Covering  power  of  inert  pigments. 


Brick-dust  is  used  to  a  large  extent  to  adulterate  red  lead  and  other 
red  paints ;  even  the  low-price  iron  oxides  do  not  escape  it,  particularly 
the  brighter-colored  copperas  oxide.  It  tones  them  down  to  many 
required  trade-shades.  Care  is  not  always  exercised  to  grind  only 


188      INERT  PIGMENTS,   OR  ADULTERANTS.     FELDSPAR. 

the  hard-burned  bricks  for  the  pigment,  hence  many  of  the  samples 
are  not  much  better  than  a  dried  clay  or  red  chalk. 

Prof.  Mallett's  experiments  with  paints  composed  of  pulverized 
hard-burned  red  tiles,  iron  oxide,  and  red  lead  were  favorable  in  cer- 
tain proportions  of  the  several  substances,  and  decidedly  unfavorable 
with  other  proportions  of  the  same  ingredients,  whether  applied 
to  wood  or  iron.  In  general  the  tiles  added  nothing  to  the  quality  of 
the  paint,  only  reduced  the  cost  of  it.  They  are  practically  unoxidiz- 
able  by  atmospheric  influences  or  weak  acidulous  solutions,  and  are 
electronegative  to  metals  or  their  oxides.  In  any  electrolytic  action 
set  up  by  any  cause  in  a  paint  coating  of  which  brick-dust  is  a  part, 
the  tendency  will  be  to  decompose  the  other  pigments,  possibly,  before 
electrolysis  is  developed  in  the  covered  iron  surface.  (See  page  53.) 

Feldspar.  Specific  gravity,  2.5  to  2.8.  Decomposed  mica,  granite, 
gneiss,  and  most  forms  of  basalt  form  this  class  of  adulterants,  and 
are  all  inclined  to  further  decomposition  on  exposure  to  the  weather. 
Many  of  the  fire-clays  used  in  the  manufacture  of  fire-brick  are  broken 
down  and  decomposed  feldspars.  Its  use  in  the  composition  of  a 
pigment  is  of  the  most  unreliable  character  in  all  respects.  It  is  as 
poor  a  substance  for  an  adulterant  as  nature  furnishes.  Mixed  paints 
frequently  contain  15  to  20  per  cent  of  it.  Feldspar  carries  a  large 
amount  of  water  loosely  held  and  frequently  acidulated,  also  sand, 
etc.  It  is  easily  whipped  up  in  the  oil  and  mixes  well  with  graphite  for 
dark-colored  paints. 

Gypsum  (Sulphate  of  Lime).  Natural  mineral  (hydrated),  CaO.SOs 
+H2O;  calcined,  CaO.SO3.  Specific  gravity,  2.4  to  2.8.  The  nat- 
ural mineral  ground  is  the  plaster  that  farmers  use  on  their  crops 
to  attract  and  condense  atmospheric  moisture.  Calcined  to  expel 
the  one  atom  of  water  held  in  its  natural  state,  it  becomes  the 
common  plaster  of  Paris,  used  for  the  hard  finish  of  plastered  walls 
of  buildings.  The  process  of  grinding  is  supposed  to  drive  off  the 
one  atom  of  water  it  holds  naturally,  by  the  heat  developed  in  the 
dry  grinding-mill,  but  this  is  soon  replaced  upon  a  short  exposure 
to  the  atmosphere,  and  when  used  for  the  hard  finish,  it  must  be 
heated  again  to  dispel  it,  or  a  porous  wall  coating  results.  A  hydrated 
sulphate  of  lime  contains  over  18  per  cent  of  water. 

When  used  in  the  composition  of  a  paint,  it  must  be  thoroughly 
calcined,  and  is  so  specified  by  parties  who  allow  its  use.  Neglect 
of  this  carries  the  moisture  into  the  paint,  where  some  portion  of  the 
sulphur  element  in  the  gypsum  is  released,  and  combining  with  the 


INERT  PIGMENTS,   OR  ADULTERANTS.    GYPSUM.          189 

fatty  acids  in  the  oil,  sometimes  causes  the  paint  "to  liver,"  a  phe- 
nomenon familiar  to  all  painters,  but  not  always  attributed  to  the 
right  cause,  viz.:  too  much  of  a  sulphurous  adulterant. 

Gypsum  grinds  easily,  is  opaque,  and  incorporates  readily  with 
most  pigments  and  the  vehicle.  It  is  not  liable  to  set  or  settle  in  the 
paint-bucket  or  package,  and  probably  is  the  best  of  all  the  inert 
substances  to  use  as  an  adulterant. 

The  extra  atom  of  sulphur  in  the  natural  mineral  other  than  that 
necessary  to  form  the  sulphurous-acid  compound  is  strongly  com- 
bined, but  if  the  mineral  or  ground  pigment  is  calcined  at  a  tempera- 
ture higher  than  that  necessary  to  release  the  one  atom  of  water, 
the  sulphuric-acid  atoms  are  excited  to  a  degree  that  will  afterward 
manifest  the  same  destructive  properties  as  the  same  element  does 
in  any  other  pigment  or  substance,  and  as  noted  above  in  the  "liver- 
ing"  of  the  green-paint  coating. 

A  synthetical  sulphate  of  lime  is  supposed  to  be  formed  when 
iron  ore  is  roasted  in  a  furnace  in  contact  with  a  quantity  of  carbon- 
ate of  lime.  The  roasting  process,  besides  driving  off  the  moisture 
in  both  the  iron  ore  and  carbonate  of  lime,  and  a  part  of  the  sulphur 
in  the  iron  ore,  excites  the  remaining  atoms  of  sulphur  to  leave  the 
ore,  and  combines  with  the  now  anhydrous  carbonate  of  lime,  CaO, 
and  forms  the  anhydrous  sulphate  of  lime,  CaO.S03,  described  above. 
The  process  is  an  unsatisfactory  one,  as  the  carbonate  is  generally 
added  in  great  excess  of  the  amount  needed  to  effect  the  chemical 
combination  with  the  sulphur  to  form  the  sulphate.  When  the  roasted 
iron  ore  is  removed  from  the  furnace  to  be  ground,  the  sulphate  is 
not  distinguishable  or  separable  from  the  uncombined  carbonate  of 
lime,  and  both  are  ground  with  the  ore  and  appear  as  adulterants, 
that  may  be  5,  10,  or  20  per  cent,  or  as  much  as  can  be  unloaded 
upon  the  consumer. 

In  whatever  amount  these  lime  products  are  present  in  the  iron- 
oxide  pigment,  they  are  both,  like  the  oxide,  anhydrous,  hygroscopic, 
and  readily  attract  moisture,  frequently  5  per  cent  in  oxide  pig- 
ments that  have  been  made  for  some  time. 

The  synthetical  sulphate  of  lime  formed  in  the  roasting  of  cop- 
peras, as  described  in  the  preparation  of  that  substance  for  an  iron- 
oxide  pigment,  is  of  the  same  character  as  that  from  roasted  iron 
ore,  only  it  carries  more  loosely  combined  sulphuric  acid  in  its  com- 
position, as  is  denoted  by  the  brighter  color  of  the  pigment.  Its 


190          INERT  PIGMENTS,  OR  ADULTERANTS.    KAOLIN. 


effect  upon  the  paint  coating  is  the  same,  and  is  not  conducive  to 
any  permanency  of  color  or  protective  qualities. 

Kaolin  (American  Terra  Alba).  A  clay  of  the  same  class  as  pipe- 
clay, China  clay,  potters'  clay,  etc.  The  reddish  color  of  the  latter 
being  due  to  the  iron  and  other  metallic  oxides.  Specific  gravities, 
2.58  to  2.76. 

Their  general  composition  is  as  follows: 


Substances. 

*%£?• 

Potters'  and 
China  Clay, 
Light  and  Dark. 

Terra-  Alba, 
White  and  Gray. 

Alumina     .                 ... 

Percentages. 
23.  25  to  21.  28 
72.23  "  65.49 

Percentages. 
23.  25  to  21.28 
73.33  "  64.95 

Percentages. 
28.51  to  15.50 
67.50  "  49.65 
22.40  "     1.52 
0.17  "  traces 
3.70  "     2.05 

8.  58  to    0.42 

Silica                        

Lime  

Magnesia 

Oxide  of  iron 

1.26  to    2.54 
7.26"     1.78 
4.72  "  traces 
4.00"     1.30 

Alkaline  earths 

Sulphate  of  lime  

Moisture.  .     .      .        

12.  00  to    4.00 

All  of  the  pigment-clays  grind  greasy,  and  are  as  easily  broken 
down  and  decomposed  by  the  weather  as  any  of  the  clays  in  building 
brick  or  mud  from  a  mill-pond. 

Mixed  with  talc,  the  clays  are  supposed  to  add  some  advantage 
to  pigments  of  a  granular  character.  What  that  advantage  is  the 
author  has  never  been  able  to  ascertain,  but  he  knows  they  cause 
paint  to  peel  or  crack. 

Marl.     Specific  gravity,  2.4.     It  is  composed  of: 

Carbonate  of  lime 50  per  cent. 

Silica 12    "      " 

Alumina 32    "      " 

Oxides  of  iron  and  manganese.  ...  2    "      " 
Water 4    "      " 

100  "     " 

Its  gray  color  prevents  its  use  as  an  adulterant  of  the  white  paints, 
but  in  the  tinted  colors  it  is  used  quite  as  freely  as  kaolin  or  chalk. 
It  is  difficult  to  pulverize  on  account  of  its  greasy  nature.  It  saves 
oil,  but  causes  the  coating  to  chalk  or  peel  on  a  short  exposure  to 
atmospheric  influences. 


INERT  PIGMENTS,  OR  ADULTERANTS.     OCHRE.  191 

Ochre.  A  yellow  clay  containing  from  8  to  15  per  cent  of  water 
loosely  held  with  large  amounts  of  sand,  also  marked  quantities  of 
iron  oxide  and  sulphur.  When  moderately  heated,  the  lower  grades 
of  ochre  contain  sulphur  enough  to  change  their  color  to  a  pink  or 
low  red. 

The  common  grades  were  formerly  used  as  a  coating  for  tin  roofs. 
They  were  always  subject  to  blistering,  from  the  large  quantity  of 
water  they  carried  into  the  paint.  It  is  an  adulterant  without  a 
single  inert  element  in  it,  and  its  presence  in  a  paint  is  generally 
accompanied  by  as  poor  a  quality  of  oil  as  it  is  a  pigment. 

Silica  (Si.SO2).  Specific  gravity,  1.9,  2.5,  2.8.  Is  a  sulphate  of 
silicon  containing  one  atom  of  silicon  combined  with  one  atom  of 
sulphurous  acid.  It  is  found  in  crystals  of  different  degrees  of 
translucency,  and  forms  a  component  part  of  all  metallic  ores; 
of  iron  ore,  frequently,  50  per  cent.  (See  Analyses  of  Iron  Ores, 
Chapter  III.) 

In  its  natural  form  it  is  one  of  the  most  imperishable  of  all  min- 
erals. It  grinds  hard  and  splintery,  and  is  difficult  to  reduce  to  the 
fineness  required  for  a  pigment.  Manufacturers  of  silica  products 
subject  the  crystals  to  a  bright-red  heat  and  quench  them  in  water, 
causing  them  to  fracture  and  grind  more  easily.  However,  the 
calcination  drives  off  a  part  of  the  sulphuric  acid  and  renders  the 
silica  caustic, — the  latter  condition  is  not  a  favorable  one  for  any 
pigment,  inert  or  basic. 

Silica  is  not  affected  by  sulphurous  gases,  acids,  or  alkalies. 
Floated  silica  or  silex  makes  an  excellent  wood-filler  paint.  All 
silicas  are  difficult  to  hold  up  in  oil,  and  on  settling,  cake  very  hard. 

Sand,  generally  supposed  to  be  the  same  substance  as  silica,  is, 
however,  of  quartz  formation  as  an  oxide  of  silicon,  specific  gravity 
1.44  to  1.76,  only  about  two-thirds  the  weight  of  silica.  It  grinds 
hard  and  splintery,  or  in  an  irregular  crystalline  form,  and  is  difficult 
to  grind  to  a  pigment. 

Neither  silica  nor  sand  mix  with  other  pigments,  except  in  a  purely 
mechanical  manner,  differing  according  to  the  specific  gravities  of 
the  several  substances  incorporated  together.  They  have  no  affinity 
for  the  vehicle,  are  not  in  their  pulverized  form  absorbent  of  moisture, 
except  to  a  very  small  amount.  From  their  indestructible  nature, 
they  form  the  electro-negative  element  or  centres  to  determine  the 
electrolytic  action  always  present  in  the  decay  of  a  paint  coating. 
Their  use  as  adulterants  of  mixed  paints  is  greater  than  any  manufac- 


192     INERT  PIGMENTS,  AMOUNTS  MANUFACTURED,  ETC. 

turer  of  paints  will  acknowledge.  The  covering  power  of  silica  is 
shown  by  Fig.  29. 

Fine  sand  is  used  for  an  application  to  green  paint  on  exterior 
surfaces  with  a  view  to  affording  an  extra  protection  from  atmos- 
pheric effects.  It  in  all  cases  hastens  the  decay  of  the  paint.  It 
holds  the  moisture,  dust,  and  other  organic  substances,  and  their 
easy  and  early  decomposition  results.  Blisters  form  more  readily 
under  a  sand-coated  paint  than  with  a  paint  alone. 

Talc  (Steatite  or  Soapstone).  Specific  gravity,  2.65  to  2.8. 
Grinds  greasy  and  flaky,  is  inclined  to  cause  a  paint  to  peel,  and  is 
repellent  to  the  oil.  Its  use  with  kaolin  has  been  given.  It  is  used 
for  a  special  adulterant  of  flake  and  other  graphitic  carbons  (see 
Chapter  XIII).  As  a  pigment  it  has  no  qualities  whatever.  As  an 
adulterant  its  function  is  to  enable  some  objectionable  substance  to 
attempt  a  mission  that  could  be  better  performed  by  a  straight  pig- 
ment. 

The  above  list  does  not  exhaust  the  substances  known  as  adul- 
terants or  miscalled  "inert"  pigments.  As  protective  coverings  for 
ferric  bodies,  the  protective  effects  of  the  inert  pigments  in  use  with 
the  basic  pigments  will  be  noted  in  the  paint  tests  made  to  determine 
their  value  (see  Chapters  XXIX  and  XXX).  Their  covering  or 
coloring  powers  are  shown  by  Fig.  29. 

The  following  amounts  of  inert  pigments  were  produced  and  used 
in  the  United  States  (averaged  for  the  years  1898  to  1901) : 

Barytes,  all  grades,  124,000  short  tons.  Cost  of  the  crude  mineral, 
$3.30  to  $3.50  per  ton. 

Imported  barytes,  1400  tons,  including  some  floated.  Cost  of 
the  manufactured  article,  $10.50  to  $11.00  per  ton. 

Feldspar  mined  in  the  United  States  for  all  purposes  in  1898  to 
1901  averaged  27,280  tons  and  cost  from  $3  to  $6  per  ton. 

Ground  slate  and  shale  for  pigments  averaged  4,700  short  tons, 
value  from  $9.50  to  $10.00  per  ton. 

Of  soapstone  ground  for  pigments  and  foundry  use,  there  were 
produced  9000  tons  yearly.  Value  8£  to  9  cents  per  pound. 

Of  gypsum  calcined,  for  all  purposes,  280,000  short  tons  were  pro- 
duced in  1901,  cost  $3.50  to  $3.90  per  ton. 

Crude  gypsum  costs  $1.20  to  $1.25  per  short  ton. 


CHAPTER  XIX. 

SPIRITS   OF   TURPENTINE. 

THE  composition  of  spirits  or  oil  of  turpentine  is  C10H16.  Specific 
gravity,  0.86  to  0.88,  with  a  boiling-point  always  near  160°  F.  The 
several  varieties  of  commercial  turpentine  obtained  from  the  sap  of 
fir-  and  pine-trees  are  more  or  less  viscid  solutions  of  resins  in  a  vola- 
tile oil,  the  proportions  of  these  constituents  varying  according  to 
the  source  and  age  of  the  turpentine-tree.  Some  kinds  are  clear  and 
homogeneous;  others  are  more  or  less  turbid,  holding  in  suspension 
granule-crystalline  masses,  which  gradually  settle  to  the  bottom,  and 
are  known  to  painters  as  "  drops." 

Spirits  of  turpentine  is  the  product  of  the  first  distillation  of  the 
crude  gum,  and  consists  of  about  one-third  spirits  and  two-thirds  water. 
It  requires  about  twenty-five  barrels  of  crude  gum  to  make  two 
barrels  of  the  spirits  of  turpentine,  that  when  redistilled  is  known 
as  refined  or  oil  of  turpentine. 

The  principal  supply  of  turpentine  is  obtained  from  the  American 
long-leaf  yellow  pine-tree,  Pinus  palustris  (P.  australis);  also  from 
the  loblolly-pine,  P.  tceda;  all  products  of  the  southern  part  of  the 
United  States,  where  the  Coniferae  are  the  principal  trees.  There  are 
many  varieties  of  the  Coniferse,  and  all  yield  gums  available  for  distil- 
lation into  turpentines  and  resins. 

Turpentine  consists  chiefly  of  a  hydrocarbon  oil  (C10  H16)  and  a 
resin  called  "Colophony"  (C^H^O.,).  Specific  gravity,  1.07  to  1.08. 
It  softens  at  155°  to  175°  F.  and  melts  between  194°  and  212°  F. 
The  spirits  of  turpentine  constitutes  about  17  per  cent  of  the  yellow 
pine-tree  sap  or  crude  gum.  The  Maritime  pine  furnishes  about  24 
per  cent  of  spirits  of  turpentine. 

The  exuded  gum  from  all  of  the  turpentine-trees  is  a  yellowish, 
opaque,  tough  mass,  brittle  and  crumbly  when  cold,  crystalline  in 
the  interior,  and  of  a  characteristic  taste  and  odor,  a  distinguishing 
feature  in  all  types  of  the  "  turpens,"  designated  as  the  terebinthic 
odor.  The  commercial  oils  of  turpentine  are  as  follows: 

193 


194  SPIRITS  OF  TURPENTINE 

The  German,  derived  chiefly  from  the  Pinus  sylvestris  (Scotch  fir), 
P.  nigra,  and  P.  rotundata. 

The  English,  from  the  American  or  Carolina  Pinus  australis  or 
P.  tceda. 

The  French,  or  Bordeaux,  from  the  Pinus  maritima,  resembles 
the  American  turpentine  in  appearance,  odor,  and  taste,  and  is  con- 
sidered to  be  the  quickest  drier. 

The  Strasburg  is  the  product  from  the  Abies  pectinata  and  from 
the  spruce  fir,  Abies  excelsa. 

The  Venice  is  the  product  from  the  Terebinthina  venita,  or  the 
larch,  Larix  europea. 

The  Hungarian  is  from  Pinus  pumilio. 

The  Carpathian,  from  the  Pinus  cembra,  has  a  bitter  taste. 

The  Cyprian,  Syrian,  or  Chio,  obtained  in  Chio,  is  from  the  Pistacia 
terebinihus. 

Templin,  or  pine-cone  oil,  is  furnished  from  the  cones  of  the  Pinus 
pumilio  and  the  Abies  pectinata. 

The  Canadian  oil  or  Canada  balsam,  from  the  Abies  balsamea  (Balm 
of  Gilead),  furnishes  the  whitest  and  purest  of  all  of  the  turpentines. 

Related  to  the  true  turpentine-oils  are  the  two  volatile  oils  of  the 
coniferous  plants — oil  of  juniper  from  the  Juniperus  communis,  and 
the  oil  of  savin  from  the  Juniperus  sabina. 

A  characteristic  feature  in  American  turpentines  is  that  they 
polarized  to  the  right,  while  most  of  the  turpentines  from  other 
sources  polarize  to  the  left. 

The  crude  resin  from  which  the  oil  of  turpentine  is  distilled  has  a 
specific  gravity  of  0.95  to  0.98,  according  to  the  time  of  its  collec- 
tion, whether  in  the  first,  second,  third,  or  fourth  year  after  the  tree 
is  boxed,  or  during  the  time  of  collecting  the  dried  sap  in  the  first 
flow  in  the  spring,  or  the  summer,  or  later  in  the  fall.  Also  its  freedom 
from  sand,  leaves,  bark,  and  dirt;  all  of  which  are  readily  absorbed 
by  the  sticky,  drying  sap,  and  are  only  removed  in  the  process  of 
distilling  the  gum  for  spirits  of  turpentine.  Another  distillation  is 
required  to  produce  the  oil  of  turpentine  or  "turps"  of  the  painter. 

Fig.  30  shows  the  old  method  of  boxing  the  trees  to  collect  the 
crude  resin. 

In  addition  to  the  exuded  gum  from  living  trees,  turpentine  is 
also  obtained  by  the  distillation  of  the  dead  wood  from  the  long-leaf 
pine-tree  when  it  no  longer  yields  the  gum  (after  the  fourth  or  fifth 
year) ,  and  when  it  has  been  turned  over  to  the  lumber  or  cord-wood 


SPIRITS  OF  TURPENTINE. 


195 


men.  The  trees  not  fit  for  lumber,  or  unfavorably  located  for  hand- 
ling the  cord-wood,  are  cut  down  and  distilled  in  a  kiln  or  oven  similar 
to  that  used  for  the  production  of  charcoal  from  hard  wood. 


FIG.  30. — Boxing  the  turpentine-tree. 

A  cord  of  fat  pine-wood  yields  by  kiln  distillation,  according  to 
the  amount  of  the  pitchy  matter  in  it,  whether  it  is  body  wood  or 
from  the  limbs,  tops,  or  decayed  wood,  the  following  products: 

Turpentine  crude  oil 22  to    26  gallons  \ 

Pyroligneous  acid 86  "     90       "        [  1150  to  1200  pounds. 

Pine-tar 118  "  122       "        ) 

Charcoal 54  "     58  bushels — 2200  to  2400  pounds. 


196 


SPIRITS  OF  TURPENTINE. 


Many  commercial  turpentines  contain  acid.  They  are  generally 
the  products  of  kilns,  and  are  not  redistilled  to  free  them  from  the 
acids.  The  effect  of  the  use  of  turpentine  in  a  paint  or  varnish  is 
to  flatten  the  gloss  or  lustre. 

Even  with  a  pure  turpentine  not  more  than  3J  per  cent  is  admissi- 
bie  in  a  paint;  and  less  than  this  if  the  turpentine  is  poor  or  fatty. 

Pure  turpentine-oil  is  adulterated  with  crude  or  undistilled  tur- 
pentine, light-colored  resin-oil,  and  resin. 

These  adulterations  are  detected  by  the  pyroligneous  smell  and 
nauseous  after-taste  on  the  tongue  and  by  the  change  in  the  specific 
gravity.  Also  by  the  reaction  produced  by  adding  8  drops  of  strong 
ammonia  to  90  c.c.  (1.422  cubic  inch)  to  the  turpentine.  The  follow- 
ing are  the  results: 


Pure  Oil  of  Turpentine. 

Specific 
Gravity. 

Reactions  with  Ammonia. 

Pure  oil  of  turpentine  recently 
distilled.    . 

0   8678 

No  effect.  The  turpentine  evaporates 
quickly  No  residuum 

7.4409  pounds  per  gal. 

Old  pure  oil  of  turpentine  .... 
7.4534  pounds  per  gal. 

0.8693 

Solidifies  in  a  few  seconds,  forming  a 
white  crystalline  substance  with  the 
consistency  of  butter. 

Pure  turpentine  with  10  per 
cent  of  resin  spirit  

0.8784 

Forms  an  emulsion,  which  rapidly  be- 
comes clear.  The  ammonia  which 

7.3496  pounds  per  gal. 

separates  has  a  pale-yellow  color. 

Pure  turpentine  with  10  per 
cent  of  undistilled  turpen- 
tine                        

0.8784 

Forms  an  emulsion  which  becomes 
clear  on  standing,  gives  a  semi-trans- 
parent sediment  of  a  bluish  color,  the 

7  .  3496  pounds  per  gal. 

liquid  above  being  colorless. 

Pure  turpentine  with  10  per 
cent  of  re  pin       .               ... 

0.8831 

Each  drop  of  ammonia  appears  to  solid- 
ifv  as  it  falls  into  the  oil.  On  agita- 

7 .  3686  pounds  per  gal  , 

tion  the  whole  solidifies  hi  to  a  consis- 
tent transparent  mass. 

Characteristics  of  Oil  of  Turpentine. 

Pure  oil  of  turpentine  has  the  composition  of  C10  H16,  and  at  a 
specific  gravity  of  0.839  weighs  7  pounds  per  gallon.  At  60°  F. 
the  gravity  is  31°  Baume,  and  it  weighs  7  pounds  per  gallon.  At 
60°  F.  pure  turpentine  should  weigh  not  less  than  6.802  nor  more 
than  7.278  pounds  per  gallon. 

Benzine  at  60°  F.  has  a  gravity  of  65°  to  72°  Baum£  and  weighs 
5|  to  6  pounds  per  gallon.  The  hydrometer  test  for  benzine  is  62° 


SPIRITS  OF  TURPENTINE.  197 

Baume.  Any  benzine  or  light  kerosene-oil  added  to  turpentine  will 
raise  the  degree  to  some  point  between  32°  and  65°  B.  36°  to  38°  B. 
should  be  the  limit  of  acceptance  for  turpentine. 

Turpentine  adulterated  with  mineral  oil  will  leave  a  stain  on  a 
blotting-paper  filter. 

An  average  quality  of  turpentine  boils  at  320°  to  350°  F.  and 
has  a  flash-point  of  103°  or  104°  F. 

Crude  turpentine  resin  boils  at  316°  F. 

Crude  turpentine  resin,  specific  gravity  0.98  to  0.95,  is  dissoluble 
in  water,  but  readily  soluble  in  ether  or  spirits  of  turpentine  and 
in  six  parts  of  alcohol.  The  alcoholic  solution  has  an  acid  reaction. 

Bromine  and  iodine  act  violently  upon  it.  When  brought  into 
contact  with  a  mixture  of  nitric  and  sulphuric  acids  it  takes  fire. 
Turpentine  is  a  solvent  of  all  oils  and  resinous  gums  at  ordinary  tem- 
peratures, but  some  of  the  fossil  resins  require  a  low  heat  to  aid  its 
action. 

Adulterants  of  Turpentine. 

Kiln-distilled  spirits  of  turpentine  contains  pyroligneous  and 
other  acids,  specific  gravity,  0.80  to  0.84. 

Crude  petroleum,  specific  gravity,  38°  to  48° Baume;  weight,  7.00  to 
6.62  pounds  per  gallon. 

Benzine,  specific  gravity,  54°  to  62°  B.;  weight,  6.39  to  6.10 
pounds  per  gallon. 

Naphtha,  specific  gravity,  62°  to  70°  B. ;  weight,  6.09  to  5.79  pounds 
per  gallon. 

The  pyroligneous  acid  in  turpentine  distilled  from  dead-fat  pine- 
wood  settles  out  partially  after  standing,  but  commercial  brands  not 
redistilled  still  contain  some  amount  of  the  acid. 

Commercial  spirits  of  turpentine  has  a  specific  gravity  of  32° 
Baume.  Any  addition  of  petroleum  of  40°  B.  will  be  shown  by  the 
rise  in  the  hydrometer;  each  3  to  5  per  cent  of  petroleum  added 
causes  a  rise  of  1°  B.  on  the  scale.  If  the  adulterant  is  benzine  or 
naphtha,  then  the  difference  in  the  specific  gravity  is  very  marked  and 
will  at  once  determine  the  character  of  the  adulterant,  it  being  much 
lighter  than  coal-oil  or  kerosene. 

For  the  detection  of  resin  in  the  spirits  of  turpentine,  the  polari- 
scope-test  is  the  only  one  that  can  be  considered  strictly  accurate, 
but  it  is  a  delicate  one,  and  requires  experience  to  determine  results. 

A  ready  method  for  detecting  resin  consists  in  dilute  sulphuric 


11J8  SPIRITS  OF  TURPENTINE. 

acid  one  part  and  four  parts  spirits  of  turpentine;  mix  and  shake  in 
a  test-tube  and  notice  the  precipitate,  which  will  be  the  resin;  allow 
for  the  resin  normal  in  all  turpentines;  the  pure  spirits  of  turpentine 
will  be  found  on  top  of  the  fluid  in  the  tube.  The  flash-test  for  naphtha 
adulterations  consists  in  heating  the  turpentine  in  a  double  vessel 
63°  to  65°  F.  and  then  flashing  it.  If  it  ignites,  it  is  safe  to  assume  the 
mixture  contains  more  or  less  naphtha. 

The  Journal  of  Chemical  Industry,  Vol.  IX,  1890,  p.  657,  gives  a 
test  for  commercial  spirits  of  turpentine,  the  usual  adulterants  being 
naphtha,  petroleum,  resin-oil,  and  the  inferior  Russian  oil  of  turpen- 
tine. (See  also  same  Journal,  pp.  330-557.) 

The  U.  S.  Navy  Department  tests  for  turpentine  are:  A  single 
drop  placed  on  white  paper  should  completely  evaporate  at  a  tem- 
perature of  70°  F.  without  leaving  a  stain. 

A  few  drops  on  a  piece  of  white  paper,  hung  vertically  before  the 
light,  if  the  turpentine  is  pure  and  well  distilled,  should  leave  no  mark 
after  5  to  7  minutes.  A  faint  mark  indicates  the  presence  of  resin 
due  to  imperfect  distillation.  If  a  gray  mark  remains  for  an  hour  or 
more,  it  indicates  kerosene  or  other  petroleum  oil.  If  a  greasy  mark 
remains  over  10  to  12  hours,  petroleum  is  present  in  large  quantities. 

It  requires  from  680,000  to  1,000,000  acres  or  1060  to  1560  square 
miles  of  forest  to  supply  the  turpentine  products,  whose  value  is  from 
$8,000,000  to  $8,600,000  yearly.  Both  the  export  and  home  demand 
are  increasing  from  5  to  8  per  cent  yearly,  and  the  forest  supply 
for  tapping  is  decreasing  in  more  than  an  arithmetical  ratio  of  these 
amounts. 

The  unit  of  product  for  a  turpentine  crop  is  10,000  boxes 
of  2500  trees  from  100  to  300  acres  of  forest,  according  to  the 
size  of  the  trees,  or  an  average  of  15  trees  per  acre.  When  the 
lumber  is  exhausted  and  the  cord-wood  is  cut  out,  there  remains 
about  one-half  a  cord  of  wood  per  tree  available  for  kiln  distillation. 
This  will  yield  about  12  gallons  of  crude  turpentine  spirits  that  would 
redistill  to  about  10  gallons  of  the  oil  of  turpentine  per  tree.  This 
amount,  if  it  all  could  be  collected  and  distilled,  would  yield  about 
6  times  the  yearly  demand  of  22,000,000  gallons.  But  95  per  cent 
of  this  supply  of  wood  would  be  used  for  saw-mill  fuel,  cord-wood, 
waste,  and  be  unavailable  on  account  of  location,  or  standing  as  dead- 
wood  forest.  The  latter  is  a  fruitful  source  of  the  forest  fires  that 
annually  destroy  from  3000  to  5000  acres  of  this  valuable  timber. 
Hence  but  5  per  cent  would  find  its  way  to  the  kiln,  and  furnish 


SPIRITS  OF  TURPENTINE.  199 

about  25,000,000  gallons  of  turpentine,  or  a  little  more  than  the 
present  (1903)  requirement,  if  the  supply  came  from  this  source 
alone. 

When  the  long-leaf  pine  forests  have  practically  disappeared, 
they  will  have  to  be  carefully  gleaned  once  and  for  all  in  order  to 
produce  a  quantity  of  turpentine  equal  to  the  present  demand  for 
one  year. 

A  barrel  (240  to  260  pounds)  of  the  crude  turpentine  resin,  when 
distilled,  yields  from  10  to  11  gallons  of  turpentine  spirits  that  need 
to  be  redistilled  to  afford  a  pure  oil  of  turpentine.  About  one-half 
or  five-eighths  of  a  barrel  of  resin  (170  to  190  pounds)  is  also  a  re- 
sult of  this  distillation.  This  resin  is  redistilled  for  resin-oils  of  a 
number  of  grades,  whose  specific  gravities  range  from  0.960  to  0.9910. 
It  also  furnishes  sixteen  recognized  grades  of  commercial  resins ;  those 
known  as  W.  W.  (water-white),  W»  G.  (window  glass),  are  the  finest 
and  most  valuable,  being  produced  from  the  first  year's  run  or  virgin 
sap.  Each  subsequent  year  of  the  four  or  five  years  that  the  trees  run 
resin,  an  inferior  quality  is  produced,  that  is  graded  N.  (very  clear); 
then  M.  L.  K.,  J.  H.  to  A.,  the  latter  being  almost  black,  and  rated 
commercially  as  pitch,  specific  gravity,  1.15. 

The  flow  of  resin  from  the  freshly  boxed  or  virgin  cut  trees  is  from 
250  to  350  barrels  of  240  to  260  pounds  for  the  first  year,  and  requires 
100  to  200  acres  of  forest;  the  flow  decreasing  to  48  or  60  barrels  in 
the  fourth  year,  that  furnishes  the  poorer  grade  of  crude  resin,  that 
contains  but  little  turpentine. 

The  action  of  turpentine  as  a  drier  for  paint  or  varnish  is  to  form 
the  peroxide  of  hydrogen  from  the  air  that  renders  them  non-drying 
except  upon  the  surface. 

Turpentine,  by  absorbing  oxygen  from  the  air  as  it  stands  in  the 
barrel,  is  liable  to  become  "fatty"  (C10.H16.O2)  with  age,  and  cannot  be 
properly  corrected  except  by  redistilling.  The  use  of  such  turpentine 
in  a  paint  is  to  render  it  " tacky."  Painters  resort  to  the  use  of  ben- 
zine to  correct  this  fatty  condition,  but  it  is  detrimental  to  the  life  of 
the  paint  and  to  its  gloss. 

Fatty  turpentine  evaporates  slowly  on  blotting-paper  and  leaves 
a  stain  upon  it. 

A  drop  of  turpentine  allowed  to  spread  itself  slowly  down  a  piece 
of  glass  coated  black  upon  the  other  side  of  the  plate  will  show  a  bluish 
tinge  at  the  edges  if  petroleum  is  present  even  to  the  amount  of  5  per 
cent. 


200  SPIRITS  OF  TURPENTINE. 

Adulterations  of  turpentine  with  resin-oil  are  shown  where  the 
residue  left  after  evaporating  a  small  quantity  in  a  saucer  is  of  a 
sticky  nature  and  resinous  odor  after  it  is  ignited. 

The  use  of  tank-cars  that  have  been  used  to  transport  crude  petro- 
leum is  responsible  for  a  great  deal  of  the  impure  oil  of  turpentine. 
The  crude  oil  of  turpentine  thus  transported  and  carelessly  redistilled 
will  carry  over  enough  of  the  petroleum  to  sensibly  raise  the  specific 
gravity  of  the  turpentine. 

From  a  large  number  of  tests  of  commercial  turpentines  by  various 
State  associations  of  painters,  and  by  individual  painters  and  experi- 
menters, the  general  result  appears  to  be  that  50  per  cent  of  the 
samples  showed  .adulterations  ranging  from  5  to  20  per  cent.  There 
are  no  penalties  for  the  adulteration  of  either  turpentine-  or  linseed- 
oil,  and  when  adulterations  are  present  in  any  form  or  amount,  gen- 
erally, the  detection  of  them  is  beyond  the  power  of  the  ordinary 
purchasing  agent  or  painter. 

The  Secretary  of  Agriculture  for  the  United  States  for  the  year 
1890  reports  that  at  the  present  rate  of  consumption,  the  forests  of 
the  long-leaf  or  turpentine  pine  will  be  exhausted  in  from  8  to  10 
years.  Practically  the  yellow-pine  forests  of  North  and  South  Carolina 
are  exhausted,  and  the  production  of  turpentine  and  resin  is  now 
centred  in  Georgia,  Alabama,  and  Florida.  The  belt  of  long-leaf 
pine  timber  extends  about  150  miles  inland  from  the  seacoast  across 
the  above  States  to  the  Mississippi  River.  Texas  has  been  com- 
paratively denuded  of  the  yellow  pine. 

Where  the  supply  of  turpentine  and  resin  will  come  from  when 
these  forests  are  extinct,  is  an  unsolved  problem.  The  second  growth 
of  timber  following  the  pine  appears  to  tend  toward  the  scrub-oaks 
and  non-resinous  trees — cedars,  etc. 

Fig.  31.  shows  the  modern  or  improved  method  of  scarfing  the  tur- 
pentine-tree and  collecting  the  sap,  as  distinguished  from  boxing 
the  tree. 

Over  75  per  cent  of  the  turpentine  produced  in  the  United 
States  is  exported.  Europe  has  no  yellow-leaf  pine  forests  that 
furnish  any  great  amount  of  turpentine.  Norway,  Sweden,  and 
Russia  furnish  resins  from  the  other  pine  varieties  of  the  Coniferse, 
but  they  rate  low  in  the  amount  of  turpentine  they  contain  as  com- 
pared with  the  American  or  hot-belt  growth  of  the  long-leaf  yellow 
pine. 

The  exports  of  spirits  of  turpentine  of  all  grades  from  the  United 


SPIRITS  OF   TURPENTINE. 


201 


States  for  the  year  1897,  to  only  six  of  the  European  countries,  were 
as  follows : 

Austria 65,000  gallons. 

Belgium 2,098,810       " 

Germany 2,418,790       " 

Italy 398,710       " 

Netherlands 2,359,590       " 

Great  Britain.  .                         8,476,700       " 


Total 15,817,600 

Other  countries 682,400 


16,500,000 
United  States  consumption 5,500,000 


Total  production. 


22,000,000       "      of  turpentine,  and 
1,600,000  barrels  of  resin— 

350  to  400  pounds  per  barrel. 


FIG.  31. — Boxing  the  turpentine-tree.     New  method. 

Mr.  F.  G.  Frankorter  *  reports  "  that  the  products  of  the  pitch 
made  from  the  butt  of  the  Douglas  fir  or  Oregon  pine  are  unusually 


*  "  Science,"  July  24,  1903.     American  Chemical  Society  Journal,  1903 


202  SPIRITS  OF  TURPENTINE. 

rich  in  pitch.  They  contain  as  high  as  41.6  per  cent,  of  which 
21  per  cent  is  turpentine.  The  latter  has  about  the  same  boiling- 
point  (150°  F.)  as  that  from  the  northern  pine,  but  differs  from  it  in 
other  properties.  The  kiln  products  (turpentine,  pyroligneous  acid, 
charcoal,  pitch,  etc.)  from  one  butt  discarded  as  unfit  for  lumber 
had  a  value  of  $275."  The  tree  grows  on  any  mountainous  soil 
where  the  spruce,  hemlock,  or  any  Coniferse  grow,  and  may  be  here- 
after utilized  for  its  turpentine-supply  only.  It  grows  from  British 
Columbia  to  Mexico  in  large  forests,  the  trees  often  reaching  300  feet 
in  height.  The  bark  is  useful  for  tanning. 


CHAPTER  XX. 

CARBON  BISULPHIDE 

(CARBON  BISULPHIDE — SULPHO-CARBONIC  ACIDS). 

THIS  carbonic  anhydride  (CS2)  has  a  specific  gravity  at  32°  F.  of 
1.027  to  1.072.  At  60°  F.,  1.272  or  10.6135  pounds  per  gallon.  The 
specific  gravity  of  its  vapor  at  60°  F.  is  2.6292  to  2.644.  The 
boiling-point  of  the  commercial  article  is  118.4°  F.,  that  of  the  refined 
109.4°  F. 

It  is  composed  of  15.8  per  cent  of  carbon  and  84.2  per  cent  of  sulphur 
(CS2),  and  is  produced  by  passing  the  vapor  of  burning  sulphur  (sul- 
phurous-acid gas,  SO2)  over  charcoal  kept  at  a  red  heat.  This  is  the 
commercial  method  of  manufacture.  It  is  highly  inflammable;  its 
vapor  mixed  with  air  takes  fire  at  about  300°  F.  and  explodes  with 
great  violence.  It  is  a  colorless,  heavy,  very  volatile  liquid,  possessing 
an  acid,  pungent  taste  and  a  very  fetid  alliaceous  odor,  due  to  the 
impurities  of  8  to  10  per  cent  of  sulphur  and  hydrogen  compounds  in 
the  unrefined  product.  When  refined,  it  loses  the  nauseous  smell 
and  has  an  ether-like  odor,  but  it  is  necessary  to  keep  it  under  water 
in  air-tight  iron  vessels. 

Carbon  and  sulphur  do  not  combine  when  simply  heated  together 
in  the  solid  state,  because  the  sulphur  volatilizes  before  the  necessary 
heat  is  attained.  But  when  the  charcoal  is  ignited  to  redness  and  the 
sulphur  vapor  is  passed  over  it,  CS2  is  formed. 

Carbon  bisulphide  is  deadly  poisonous;  inhalation  of  even  very 
dilute  vapor  producing  giddiness  and  vomiting,  with  irresistible  fits  of 
weeping,  violent  pains  in  the  legs,  and  a  collapse  of  all  the  bodily 
and  mental  powers;  paralysis,  idiocy,  and  death.  Five  per  cent  of 
the  vapor  in  any  confined  space  ensures  the  death  of  all  larvae,  smaller 
mammalia,  birds,  and  reptiles.  A  solution  of  ferro-carbonate  in  car- 
bonic-acid water  is  a  partial  remedy  for  the  symptoms  on  first  attack. 

It  is  a  solvent  of  all  fats,  oils,  resins,  india-rubber,  phosphorus, 
bromine,  chlorine,  iodine,  camphor,  etc.,  and  mixes  in  almost  all 

203 


204  BISULPHIDE  OF  CARBON. 

proportions  with  alcohol,  ether,  benzine,  and  all  the  fixed  and  volatile 
oils. 

It  is  used  to  extract  the  oil  from  seeds,  particularly  linseed, 
which  is  heated  and  pressed  to  remove  some  of  the  oil  before  being 
submitted  to  the  action  of  the  bisulphide.  The  residue  cake  contains 
only  2  per  cent  of  oil  and  about  7  per  cent  of  water,  while  the  cake 
from  the  ordinary  process  of  manufacturing  linseed-oil  from  the 
steamed  linseed  contains  9  per  cent  of  oil  and  nearly  15  per  cent  of 
water.  The  oil  so  expressed  is  of  good  color,  but  contains  more 
mucilage  and  less  of  the  glyceride  element. 

The  loss  in  the  manufacture  of  the  bisulphide  is  about  50  per  cent 
of  the  charcoal  and  17  to  18  per  cent  of  the  sulphur. 

The  use  of  the  bisulphide  of  carbon  for  a  paint  vehicle  is  more  for 
the  cheaper  grades  of  roofing  or  color  paints  and  for  wooden  struc- 
tures of  minor  importance  than  for  the  better  grade  of  house  or  ferric 
paints,  though  in  many  of  the  latter  it  is  used  freely,  judging  from 
the  odor.  Its  use  is  simply  as  an  adulterant  of  the  oil  and  to  cause  a 
quick  drying  of  the  paint,  and  wherever  used  it  may  be  considered  to 
accompany  a  cheap  oil,  and  the  grade  of  the  pigments  mixed  with  it 
will  in  general  be  as  low  as  the  vehicle. 

Like  benzine  driers,  it  sensibly  lowers  the  temperature  of  the 
surface  of  the  body  being  covered,  and  in  cool  or  damp  locations  this 
reduction  is  often  enough  to  reach  the  dew-point  and  cause  a  sweat- 
deposit  on  the  surface  of  the  paint,  causing  it  to  peel. 

There  are  special  grades  of  carbon-blacks,  or  bisulphide-of-carbon 
paints,  under  many  trade-marks,  specially  noted  in  tr*ade  literature 
for  their  excellence  as  coatings  for  brine,  ammonia,  refrigerating  and 
brewers'  tanks  and  barrels.  In  some  of  these  the  paint  appears  to  give 
good  results.  Nearly  all  of  these  paints  are  simply  asphalt  or  natural 
bitumen,  refined  more  or  less,  and  a  bisulphide-of-carbon  vehicle  con- 
taining little  if  any  linseed-oil.  They  evaporate  quickly  and  leave 
the  bitumen  coating  behind,  and  probably  coat  the  surface  more  thor- 
oughly than  is  possible  to  apply  bitumen  hot  or  in  any  other  manner. 

For  painting  galvanized  iron,  the  bisulphide  of  carbon  appears  to 
be  of  merit;  at  least  the  coatings  containing  some  amount  of  bisulphide 
either  as  the  principal  vehicle  or  as  a  drier  do  not  peel  as  readily  as 
oil  paints  of  similar  color  and  pigments.  This  favorable  point  is 
more  marked  in  the  case  of  the  brownish-black  or  full-black  paints, 
and  is  probably  due  to  the  bisulphide  element  dissolving  the  greasy 
coating  of  the  sal-ammoniac  soap,  that  forms  on  the  surf  ace  of  the  gal- 


BISULPHIDE  OF  CARBON.  205 

vanized  sheet  in  the  process  of  galvanizing.  The  presence  of  this 
soapy  coating  prevents  the  oil-paint  coating  from  bonding  to  the 
metal,  and  it  dries  as  a  loose  skin,  peels  easily,  sometimes  before 
it  is  dry. 

The  bisulphide  being  a  solvent  of  all  semi-glutinous  substances 
loosens  up  this  soap  and  incorporates  it  into  the  mass  of  the  coating, 
and  the  quick  evaporation  of  the  bisulphide  leaves  it  there. 

There  are  many  instances  on  record  of  the  disastrous  results  upon 
the  health  of  the  painters  who  spread  bisulphide-of-carbon  mixtures. 
A  noted  one  is  its  use  with  maltha  (a  mineral  bitumen)  for  the  internal 
and  external  coatings  of  a  number  of  miles  of  steel-riveted  water-pipe 
mains,  where  the  application  of  this  mixture  was  attended  by  the 
disability,  insanity,  and  death  of  a  number  of  the  painters.  Its  use 
as  an  anti-corrosive  coating  for  protecting  miles  of  water-pipes  was 
wholly  experimental,  without  a  single  record  on  which  to  base  such 
an  application  of  an  untried  material,  and  especially  one  known  to 
be  decidedly  inferior  and  uncertain  for  minor  purposes.  Had  a  gill 
of  this  maltha  paint  been  spread  in  a  room  where  the  Board  of  Water 
Commissioners  and  their  Engineering  Staff  held  council  over  the  pro- 
tection of  water-pipes  from  underground  corrosion,  all  the  subsequent 
injury  to  the  painters  and  expense  of  application  and  removal  could 
have  been  avoided.  Another  coating  was  substituted  for  the  maltha, 
but  not  before  a  number  of  miles  of  the  water-mains  had  been  laid 
and  covered  in  with  no  better  protection  against  corrosion  than  that 
which  could  have  been  had  with  a  coating  of  boiled  skimmed-milk 
glue. 

In  the  open  air  bisulphide  mixtures  can  be  spread  without  material 
danger  or  discomfort  to  the  painters,  but  they  have  not  a  single  ele- 
ment of  protective  value  that  warrants  their  application  to  any 
ferric  structure  of  magnitude.  They  should  only  be  spread  on  those 
of  minor  character,  where  the  corrosion  or  decay  is  of  no  material 
importance,  and  the  question  of  the  cost  of  the  coating  and  its  tem- 
porary appearance  governs. 

Frequent  analyses  of  bisulphide  paints  show  about  50  per  cent 
of  a  low-grade  resin,  bitumen,  and  lampblack,  for  the  pigment,  with 
barytes  or  silica  added  to  give  weight.  Bisulphide-of-carbon  coatings 
brush  out  easily  and  spread  over  a  large  area,  as  the  vehicle  is  very 
thin  compared  with  that  of  a  linseed-oil  paint.  This  feature  of  itself  is 
against  their  protective  quality.  In  such  cases  the  pigments  are  but 
thinly  covered  or  embedded  in  the  vehicle,  the  quick  drying  of  which 


206  BISULPHIDE  OF  CARBON. 

by  evaporation  leaves  a  porous,  crumbly  mass  with  hardly  any  bond 
between  the  atoms  of  the  pigment  or  to  the  covered  surface.  The 
dried  coating  soon  shrinks  in  mass,  cracks  finely,  is  easily  rubbed  off 
by  the  hand,  and  requires  to  be  wholly  removed  before  repainting, 
even  to  apply  another  coating  of  the  same  compound. 

Analyses  of  dried  bisulphide-of-carbon  coatings  show  from  5  to  10 
per  cent  of  sulphur,  certainly  not  a  suitable  substance  to  recoat  with 
any  linseed-oil  paint,  unless  the  prompt  peeling  of  it  is  desired.  For 
ferric  coatings,  sulphur  in  any  form  or  amount  either  in  the  pigment 
or  vehicle  is  to  be  avoided. 

A  new  process  for  the  manufacture  of  carbon  bisulphide  by  an 
electric  furnace  has  lately  been  developed  and  patented  in  the  United 
States  by  Edward  R.  Taylor,  of  Penn  Yan,  N.  Y.*  Whether  the  new 
process  will  supersede  the  old  or  burning-charcoal  process  remains  to 
be  commercially  demonstrated.  Its  many  uses  in  the  arts  outside  of 
paints  will  always  cause  it  to  be  in  demand.  Its  present  price  of  4 
to  4^  cents  per  pound,  equal  to  42  to  45  cents  per  gallon,  leaves  nothing 
to  recommend  it  as  a  substitute  solvent  or  drier  for  turpentine  in  a 
paint. 

A  French  chemist,  M.  La  Roy,  has  suggested  an  improvement 
in  bisulphide  of  carbon  as  a  substitute  for  turpentine  in  paints  and 
varnishes.  It  is  the  chloride  of  carbon,  or  more  particularly,  the 
tetrachloride  of  carbon,  CC14.  Its  characteristics  compared  with 
turpentine  are  interesting.  It  is  a  colorless,  limpid  fluid,  specific 
gravity,  1.56  or  13  pounds  per  gallon;  boils  at  170°  F.,  being  more 
volatile  than  turpentine,  having  an  aromatic,  pungent  odor,  is  soluble 
in  alcohol  and  ether,  and  dissoluble  in  water.  The  fluid  is  not  in- 
flammable, and  dries  quicker  than  turpentine.  It  can  be  mixed  in 
all  proportions  with  all  of  the  usual  paint  solvents,  including  the 
bisulphide  of  carbon.  Varnishes  made  from  it  are  exceptionally  hard 
and  brilliant. 

In  comparison,  turpentine  (C10H16)  has  a  specific  gravity  of  0.86  to 
0.88  =  7.176  to  7.343  pounds  per  gallon,  boils  at  160°  F.,  and  is  quite 
inflammable  both  in  fluid  or  vapor.  The  tetrachloride  flattens  the 
gloss  in  oil  paints  the  same  as  turpentine,  but  adds  weight  to  the  paint. 

Tetrachloride  of    carbon  f  is  produced :    First,  by  the  action  of 

*  "  Carbon  Bisulphide  in  the  Electrical  Furnace."  Described  in  the  Electrical 
World  and  Engineer,  also  in  the  American  Gas  Light  Journal  (N.  Y.),  Jan.  6, 
1902,  p.  11.  Illustrated. 

t  Watts's  Dictionary  of  Chemistry,  Vol.  I,  p.  765. 


BISULPHIDE  OF  CARBON.  207 

chlorine  on  marsh-gas.  Second,  by  the  action  of  chlorine  on  chloro- 
form exposed  to  the  sunlight.  Third,  the  probable  commercial  proc- 
ess of  manufacture,  by  the  action  of  chlorine  on  the  disulphide  of 
carbon;  the  reaction  being,  CS2+4C12=CC14+2SC12.  Chlorine,  satu- 
rated with  the  vapor  of  the  sulphide  of  carbon  by  passing  it  through 
the  liquid,  is  passed  through  a  red-hot  tube  or  retort  filled  with  pieces 
of  porcelain,  the  outlet  of  the  retort  being  connected  to  a  receiver 
packed  in  ice.  The  condensed  yellow  mixture  of  tetrachloride  of 
carbon  and  chloride  of  sulphur  thereby  obtained  is  slowly  added  to  an 
excess  of  potash  lye  or  milk  of  lime,  the  mixture  being  agitated  from 
time  to  time  and  afterward  distilled.  The  tetrachloride  of  carbon 
passes  over,  mixed  with  some  of  the  sulphide  of  carbon.  If  too  much 
of  the  sulphide  has  been  mixed  with  the  chlorine,  or  if  the  decomposing 
heat  has  not  been  strong  enough,  the  sulphide  of  carbon  can  be  re- 
moved by  leaving  it  for  some  time  in  contact  with  the  potash  lye. 

No  estimated  cost  of  the  tetrachloride  product  is  at  present 
given,  but  its  field  of  usefulness  in  the  manufacture  of  paints  and 
varnishes,  also  as  a  special  drier,  is  favorably  indicated  from  the  few 
trials  and  experiments  thus  far  had  with  it. 


CHAPTER  XXI. 

JAPAN    DRIERS. 

JAPAN  driers  -or  japans  vary  greatly  in  their  composition  and 
are  very  erratic  in  their  action  as  drying  agents.  Specimens  from 
the  same  manufacturer,  taken  from  stock  at  different  times,  are 
widely  different  in  drying  qualities,  while  any  attempt  to  classify  the 
japans  of  different  manufacturers  is  one  of  the  vexations  of  the 
master  painters.  Probably  a  good  rule  for  painters  to  follow  in  the  case 
of  japans  is,  when  one  has  been  found  to  suit  them,  to  lay  aside  a 
sample  of  it  to  compare  with  all  future  supplies,  and  to  stick  to  that 
manufacturer  and  brand  just  as  long  as  if  comes  up  to  the  mark. 

The  general  composition  and  process  of  manufacture  of  japans 
are:  Gum  shellac  is  cooked  with  linseed-oil  in  a  varnish  kettle  until  it 
becomes  thick  and  partakes  of  the  nature  of  a  varnish.  Litharge 
and  other  substances  are  added  to  quicken  the  drying  of  the  resulting 
product.  When  the  mass  has  cooked  down  to  a  thick  substance 
called  a  "pill,"  it  is  allowed  to  cool  and  then  thinned  down  with  tur- 
pentine. Japan  is  a  light-colored  brownish-yellow  liquid  of  about 
the  consistency  of  varnish.  A  thin  surface  of  it  dries  in  from  15  to 
20  minutes.  The  care  exercised  in  the  manufacturing  process  and 
the  purity  of  all  the  materials  used,  affect  its  quality,  and  are  the 
cause  of  such  erratic  results  from  its  use. 

The  reputation  of  a  japan  or  varnish  manufacturer  counts  for 
much,  but  it  does  not  always  ensure  a  good  article,  if  the  price  governs 
the  selection. 

Formulae  for  japans  are  numerous  and  are  trade  secrets.  The 
following  are  representative  samples: 

One  gallon  cold-pressed  old  linseed-oil,  }  pound  of  D.  C.  or  L.  C. 
gum  shellac,  ^  pound  gold  litharge,  ^  pound  burnt  umber,  ^  pound  of 
red  lead,  6  ounces  sugar  of  lead.  Boil  together  with  constant  stirring 
for  4  hours,  or  until  all  of  the  ingredients  are  dissolved.  Remove 
from  the  fire,  and  when  cool  add  1  gallon  oil  of  turpentine ;  stir  well 
while  it  is  being  added. 

208 


JAPAN  DRIERS. 


209 


A  cheap  japan:  Mix  4  gallons  pure  linseed-oil,  4  pounds  each  of 
litharge  and  red  lead,  2  pounds  of  powdered  raw  umber.  Boil  slowly 
for  2  hours  and  add  by  degrees  7J-  pounds  D.  C.  gum  shellac,  and 
boil  |  hour  longer  or  until  the  ingredients  are  well  mixed.  Add  by 
degrees  1  pound  powdered  sulphate  of  zinc,  and  when  nearly  cold, 
stir  in  7  gallons  of  spirits  of  turpentine. 

The  " Bung-hole  Drier"  formulae  are  as  numerous  as  the  oil 
compounders.  The  following  represent  a  few  of  the  compounds  used: 


LEAD  OILS. 

Linseed-  or  nut-oil 1  gallon.  Linseed-  or  nut-oil  .  .  . 

Litharge 1  pound.  Litharge 

Sugar  of  lead 


1  gallon, 
i  pound. 
\  pound. 


MANGANESE  OILS. 

Linseed-oil 1  gallon.  Linseed-oil 1  gallon. 

Potassium  permanganate,  100  grains.  Pure  hydrated  protoxide 

of  manganese |  ounce. 

MANGANESE  AND  LEAD  OILS. 


Linseed-oil 1  gallon 

Umber 5  ounces. 

Gold  litharge 5  ounces. 

Red  lead 5  ounces. 

Linseed-oil 1  gallon. 

Permanganate  of  potash.  .  4  ounces. 

Acetate  of  lead 4  ounces. 


Linseed-oil 1  gallon. 

Borate  of  manganese 1  ounce. 

Acetate  of  lead 1  ounce. 

Linseed-oil 1  gallon. 

Manganese  protoxide  hy- 
drate   1  ounce. 

Red  lead  or  litharge 1  ounce. 


See  also  Boiling  Oil,  Chapter  XXIII.  For  the  effect  of  different 
driers  upon  linseed-oil,  see  Thorp's  experiments,  same  chapter. 

The  following  is  an  extract  from  a  Report  of  "Test  on  Liquid 
Driers,"  read  at  the  Sixth  Annual  Convention  of  the  Master  Painters 
and  Decorators'  Association  of  the  United  States,  held  in  Detroit, 
Mich.,  on  Feb.  11,  12,  and  13,  1890. 


Raw 
Linseed-oil 

White 
Lead 

Vandyke 
Brown 

Lamp- 
black 

Dries  in 

Dries  in 

Dries  in 

Dries  in 

Hrs.    Min. 

Hrs.    Min. 

Hrs.    Min. 

Hrs.    Min. 

1  part  Azote  drier  (trade-mark) 

to  1  part 

1         50 

1        50 

2         15 

1         50 

H        tt         tt 

tt 

"    5  parts 

2       35 

2       50 

4        20 

2       20 

tt        tt         tt 

ft 

"  10  parts 

3       40 

3       50 

6       15 

3       45 

tt        tt         tt 

tt 

"15  parts 

4       30 

5      00 

9       40 

6       20 

210  JAPAN  DRIERS. 

Brown  japan  should  mix  well  with  raw  linseed-oil  in  any  pro- 
portion up  to  15  per  cent,  and  should  stay  mixed  for  at  least  6  hours 
without  showing  sediment  or  separation,  called  "  curdling." 

When  applied  in  a  thin  film  to  a  clean,  dry  piece  of  glass  placed 
in  a  vertical  position,  the  japan  should  be  dry  to  the  touch  in  about 
2  hours,  and  should  dry  hard  without  becoming  brittle  in  6  hours. 

The  so-called  concentrated  driers  are  made  by  heating  linseed-oil 
with  lead  and  manganese  salts  or  oxides  in  excess,  until  the  product 
becomes  viscous,  like  a  sticking-plaster  or  birdlime.  Liquid  driers 
are  concentrated  driers,  thinned  out  while  hot  with  naphtha  or  spirits 
of  turpentine.  When  applied  in  a  thin  film  to  glass  and  placed  in  a 
vertical  position,  they  should  be  dry  to  the  touch  in  2  hours,  and  harden 
in  about  8  hours.  After  48  hours  the  drier  should  not  rub  off  in  the 
form  of  a  fine  powder  when  the  finger  is  rubbed  briskly  over  the  sur- 
face. Liquid  driers  should  mix  freely  with  raw  or  boiled  linseed-oil, 
turpentine,  or  benzine  in  any  proportion  without  showing  clots  or 
precipitate  after  standing  48  hours  in  the  open  air. 

Inferior  liquid  driers  can  be  recognized  by  the  odor  of  benzine 
when  the  sample  is  slightly  warmed ;  by  the  powdering  of  the  hardened 
film  when  rubbed  by  the  finger,  and  by  the  rapid  evaporation  when 
exposed  to  the  air,  with  consequent  separation  of  the  ingredients. 

The  quality  of  a  japan  depends  as  much  upon  its  cooking  as  upon 
the  quality  and  kind  of  the  materials  in  its  composition.  Too  high  a 
heat  or  too  long  exposure  to  the  heat  frequently  spoils  it. 

Gum  is  added  by  some  manufacturers  of  japans  to  harden  the  oil. 
This,  while  causing  the  japan  itself  to  dry  more  rapidly,  reduces  its 
power  to  dry  an  oil  paint.  Gum  is  a  very  uncertain  substance  in  the 
formula  of  japan  manufacturers.  It  may  mean  the  spruce  cud  of 
the  schoolgirl,  common  resin,  or  the  best  grade  of  the  fossil  resins,  over 
thirty  in  number,  with  many  varieties  in  each  number. 


CHAPTER  XXII. 

? 

FLAX-PLANT  AND   LINSEED. 

LINSEED  is  the  seed  product  of  the  Linum  usitatissimum.  This 
plant  is  a  native  of  India  or  Eastern  Asia,  and  its  cultivation  has 
existed  from  the  earliest  ages,  distinct  evidences  of  its  existence 
during  the  Stone  Age  being  preserved  to  the  present  day  in  the  rough 
and  worked  flax  made  into  bundles,  found  in  the  lake  dwellings  of 
Switzerland. 

It  is  mentioned  in  the  book  of  Exodus  as  one  of  the  products  of 
Egypt  in  the  time  of  the  Pharaohs.  Among  the  plagues  of  Egypt,  that 
of  hail  destroyed  the  flax  and  barley  crops,  "for  the  barley  was  in  the 
ear  and  the  flax  was  boiled"  (Exodus  ix.  31). 

Pharaoh  "arrayed  Joseph  in  vestures  of  fine  linen"  (Genesis  xli. 
42). 

Solomon  purchased  linen  yarn  in  Egypt  and  Herodotus  speaks  of 
the  great  flax  trade  of  Egypt. 

Numerous  pictorial  representations  of  the  cultivation  and  prep- 
aration of  flax  are  sculptured  on  the  walls  and  tombs  of  Thebes, 
showing  the  varieties  of  flax  in  the  red  and  white  flower,  the  manner 
of  pulling,  retting,  and  hachelling  as  practised  when  Jacob  dwelt  in  the 
land  of  Goshen;  and,  except  in  some  minor  particulars,  or  in  certain 
favored  locations,  are  precisely  the  same  as  practised  at  the  present 
day. 

The  crushing  of  the  seed  in  a  mortar,  grinding  it  on  a  stone  slab 
by  a  muller,  the  pressing  out  of  the  oil  with  stones,  the  seed-bag, 
the  burning  lamp  showing  that  the  ancients  knew  the  value  of  heat 
to  aid  in  the  extraction  of  the  oil,  and  the  painter  with  his  bristle  brush 
and  paint-pot  is  also  delineated. 

Flax  is  more  extensively  and  successfully  cultivated  in  Belgium 
than  in  any  other  part  of  Europe,  that  raised  in  East  and  West  Flan- 
ders (the  Coutrai  flax)  being  the  most  valuable  of  the  world's  crop 
of  this  fibre.  It  is  used  in  the  manufacture  of  Brussels  lace.  The 
crop  often  exceeds  in  value  the  land  on  which  it  is  raised,  bringing 

211 


212 


FLAX-PLANT  AND  LINSEED. 


$500  to  $750  per'  ton,  while  the  ordinary  fibre  crop  brings  $200  to 
$400. 

Prof.  Hodge's  (of  Belfast)  experiments  with  7770  pounds  of  dried 
flax  yielded  the  following  results: 

1946  pounds  of  bolls,  which  furnished  910  pounds  of  seed.  The 
5824  pounds  (52  per  cent)  of  flax  fibre,  lost  in  steeping  1456  pounds, 


FIG.  32. — Jerusalem  flax-plant  blossom.     It  grows  wild  in  Palestine,  covering 
large  areas  around  Jerusalem.     (Blue  flower.) 

leaving  4368  pounds  of  retted  stalks,  and  from  that  702  pounds  of 
finished  fibre  were  produced.  The  weight  of  fibre  was  equal  to  about 
9  per  cent  of  the  dried  flax  stalk  with  the  seed-bolls,  12  per  cent  of 
the  bolted  straw,  and  over  16  per  cent  of  the  retted  straw. 

By  Schenck's  (American)  method,  100  tons  of  the  dried  flax  straw 
gave  33  tons  of  bolls  with  27.5  tons'  loss  in  steeping;  32.13  tons  were 


FLAX-PLANT  AND  LINSEED.  213 

separated  in  scrutchings,  leaving  5.9  tons  of  finished  fibre  and  1.47 
ton  of  tow  and  pluckings. 

Generally  two  bushels  of  linseed  are  sown  per  acre,  and  the  yield 
in  finished  fibre  is  from  600  to  800  pounds,  the  market  price  of  which 
is  about  12  cents  per  pound.  The  yield  of  seed  is  from  8  to  10  bushels 
of  52  pounds,  and  is  graded  and  classified  as  to  quality  and  condition 
as  closely  as  any  of  the  grains.  The  crop  is  very  exhausting  to  the  soil ; 
potash  and  phosphoric  acid  are  the  chief  ingredients  that  the  soil 
requires  to  produce  a  good  crop  of  either  the  fibre  or  seed.  It  require^ 
from  400  to  600  pounds  of  mineral  or  phosphate  fertilizers  per  acre^ 
beside  barnyard  and  other  manures,  to  keep  the  soil  in  condition, 
and  then  only  two  or  three  crops  can  be  raised  in  succession,  when 
other  crops  must  be  substituted  for  from  5  to  8  years. 

New  England  formerly  raised  large  quantities  of  flax  for  the 
fibre,  but  the  advent  of  cotton  manufacture  soon  displaced  flax  cul- 
ture, and  this,  with  the  exhaustion  of  the  soil  and  absence  of  phosphate 
fertilizers,  caused  an  abandonment  of  the  flax  crop  in  that  part  of  the 
United  States,  early  in  the  past  century. 

America  furnishes  about  one-fourth  of  the  world's  supply  of 
linseed-oil.  The  crop  of  linseed  for  the  years  1900-1901  was  from 
16,000,000  to  17,000,000  bushels.  The  average  yield  of  oil  was  18J 
pounds  of  oil  per  bushel,  or  2.465  gallons  of  7^-pound  oil;  equal  to 
40,000,000  to  42,000,000  gallons.  In  general,  the  American  crop  is  com- 
paratively free  from  the  adulteration  of  the  wild  mustard  and  other 
acrid  seeds  that  render  the  oil-cake  almost  valueless  for  a  cattle  food. 
Though,  in  this  respect,  it  is  better  than  most  of  the  foreign  seeds, 
it  is,  however,  the  practice  for  many  seed-crushers  to  add  the  screen- 
ings from  the  linseed  and  grain  elevators  to  their  linseed  in  the  crushers, 
and  this  not  only  furnishes  a  bitter  oil-cake  but  a  poorer  oil. 

The  American  linseed  crop  is  now  chiefly  produced  by  the  North- 
western States,  where  the  rich  prairie  soil  is  favorable  for  a  heavy  seed 
crop  without  much  fertilization.  The  fibre  in  these  States,  from  its 
distance  to  market  and  the  difficulty  of  preparing  it,  is  of  minor  import- 
ance, and  the  plant  is  generally  allowed  to  fully  ripen  before  harvest- 
ing, the  flax  being  burned,  like  the  straw  from  the  wheat-fields,  to 
get  rid  of  it.  Duluth  and  Chicago  are  the  commercial  centres  for 
the  distribution  of  the  Western  linseed  crop,  the  yearly  production  of 
which  is  not  clearly  determined  at  this  date  (February,  1902)  owing 
to  the  incomplete  state  of  the  last  United  States  Census. 

The  Argentine  Republic  is  the  greatest  flax-growing  country  in 


214 


FLAX-PLANT  AND  LINSEED. 


the  world.     Flax-growing  was  begun  in  Argentina  nearly  a  hundred 
years  ago,  but  not  until  about  20  years  back  was  any  attempt  made 


FIG.  33. — Flax-plant — flower,  seed-vessel,  and  seed. 

Its  flower  is  blue.  Fig.  1  represents  a  flower  leaf  or  petal;  there  are  five  to 
each  flower,  which  is  of  a  very  regular  and  perfect  kind,  having  five  petals,  five 
pistils,  five  stamens,  five  sepals.  Figs.  2  and  3  are  sepals,  or  cup  leaves,  to  the 
flower;  Figs.  4  and  5  represent  the  seed-vessel,  with  its  tall  stamens  and  taller 
pistils;  Fig.  6  is  a  stamen;  Fig.  7  is  a  seed-vessel  cut  open,  showing  ten  seeds. 
The  stamens  fertilize  the  pistils,  the  pollen  falling  upon  the  top  of  the  pistil,  or 
probably  carried  there  by  some  busy  bee.  Within  each  of  the  pistils  (not  to 
speak  exactly)  grow  two  seeds,  as  seen  in  Fig.  7,  divided  by  a  little  wall.  Fig.  8 
is  a  ripe  seed-vessel.  Sections  of  the  seed  and  the  perfect  seed  are  seen  in  Figs. 
9,  10,  11,  and  12. 

to  raise  it  to  the  proportions  of  a  national  industry.  In  1881  some 
67,000  acres  were  planted  in  flax  in  the  province  of  Buenos  Ayres. 
The  success  of  the  venture  led  to  wider  planting  in  that  province, 


LINSEED:   SOURCES  OF  SUPPLY.  215 

and  in  Cordova,  Entre  Rios,  and  Santa  Fe.  To-day  the  crop  is  one 
of  the  most  important  in  the  country,  and  surpasses  in  magnitude 
that  of  any  other  land. 

The  plant  is  grown  only  for  the  seed,  and  as  soon  as  the  latter  is 
secured  the  straw  is  burned.  An  average  of  1000  pounds  of  seed  is 
raised  on  an  acre,  and  in  some  cases  the  yield  is  2000  pounds.  The 
export  of  flaxseed  from  the  four  provinces  named  amounts  to  500,000 
tons  a  year,  which  is  one-half  the  entire  product  of  the  world  and 
equals  54,200,000  gallons  of  oil.  Not  more  than  20,000  tons  are 
retained  for  domestic  use,  and  there  appear  to  be  no  linseed-oil  mills  in 
the  country,  as  all  the  oil  used  there  is  imported.  One  wonders  what 
the  effect  upon  the  markets  of  the  world  might  be  if  Argentina  should 
export  linseed-oil  and  cake  instead  of  raw  flaxseed,  and  could  transform 
the  straw  into  linen  thread  and  cloth  instead  of  burning  it. 

Ireland,  England,  Belgium,  and  Central  Europe  raise  the  best 
flax  for  fabric  purposes,  but  seeds  gathered  from  these  sources  being 
unripe,  furnish  poor,  watery  oil. 

Russia  has  a  large  acreage  of  flax  for  seed  purposes  and  furnishes 
about  one-sixth  of  the  world's  supply  of  linseed,  the  yield  being 
about  8  bushels  of  56  pounds  to  the  acre;  the  flax  fibre  is  of  minor 
importance,  being  woody  and  subject  to  great  waste  in  preparing  it  for 
fabric. 

Russian  seed  is  exported  for  seed  purposes  as  well  as  for  oil  extrac- 
tion. In  Russia  hempseed  is  sown  with  the  flaxseed,  and  comprises 
nearly  one-tenth  of  the  seed  crop,  but  as  this  seed  furnishes  a  siccative 
oil,  it  is  not  an  objectionable  adulterant,  such  as  the  seeds  from  the 
rape,  colza,  mustard,  and  many  other  non-drying  oil-seeds,  called 
"  flax-dodders."  The  adulteration  from  these  acrid  seeds  is  so  great 
that  the  waste  product  in  the  form  of  oil-cake,  formerly  a  valuable 
cattle  food,  is  now  so  strongly  impregnated  with  the  biting  taste  of 
these  seeds,  that  cattle  refuse  to  eat  it,  and  it  is  now  used  for  fuel  or 
fertilizing  purposes. 

India  furnishes  about  one-eighth  of  the  world's  supply  of  linseed. 
It  is  grown  as  a  mixed  crop  for  the  seed  only.  The  India  flax-plant 
has  been  deteriorating  for  over  200  years,  until  it  is  now  an  inferior 
shrub  from  12  to  16  inches  high.  The  climate  is  favorable  for  the  oil- 
producing  quality  of  the  seed.  The  white-flower  plant  produces  about 
2  per  cent  more  oil  than  the  blue-flower  variety,  also  a  sweeter  and 
softer  oil-cake.  The  edges  of  fields  devoted  to  other  crops  are  sown 
with  linseed  for  seed  purposes,  which  is  allowed  to  fully  mature  before 


216  QUALITIES  OF  LINSEED. 

gathering,  the  ordinary  linseed  crop  being  harvested  just  before  the 
seed  has  fully  matured,  and  while  it  contains  more  water  than  if  fully 
ripened. 

Rape-seed  is  sown  in  large  quantities  with  the  linseed.  Its  yield 
of  seed  and  oil  is  very  large,  and  when  refined  it  passes  as  colza-oil 
from  coleseed.  These  seed-oils  are  used  for  burning,  lubrication, 
and  in  the  manufacture  of  india-rubber  articles,  because  of  their 
non-drying  qualities.  India  is  very  prolific  in  oil-bearing  seeds;  the 
mustard  and  many  other  acrid  seeds  grow  wild,  are  very  rich  in  oil, 
and  all  are  freely  used  to  adulterate  linseed  to  an  admitted  amount 
of  10  per  cent  and  possibly  15  per  cent  more. 

The  quality  of  the  flax,  also  of  the  seed,  varies  quite  as  much  as 
any  crop  of  grain  or  vegetables,  according  to  the  locality  in  which  they 
are  raised,  the  soil,  weather,  and  other  influences  affecting  the  fibre 
or  oil,  and  the  crop  is  quite  as  exhaustive  to  the  soil  as  wheat  or  corn. 

Samples  of  linseed  grown  in  various  parts  of  the  world  and  aver- 
aged from  a  collection  of  ripe  seeds  weighed  from  48  to  52  pounds 
per  bushel,  and  the  yield  of  oil  was  quite  as  variable,  viz.: 

GALLONS  OF  T^-POUND  OIL  PER  112  POUNDS  OF  SEED. 

Best  Odessa  seed 15      to  16     gallons. 

Archangel          "    18 

Good  commercial  seed 15.5 

East  Indian  seed 17 

Sicilian  "      16 

General  results  by  a  large  crusher  for  all  seeds 14 

American  seed,  52  ^  pounds  per  bushel,  gave  26.55  per  cent  of  oil, 
or  13.87  pounds. 

Linseed  in  its  dry  state,  as  analyzed  by  Dr.  Ure,  contains: 

Oil 11 . 265  per  cent. 

Wax 0 . 146 

Soft  resin 2.488 

Resinous  coloring  matter 0 . 550 

Yellowish  coloring  matter  analagous  to  tannin 0.926 

Gum 6.154 

Vegetable  mucilage 15 . 12 

Starch 1 .48 

Gluten 2 .932 

Albumin 2.782 

Saccharine  extractive 10 . 884 

Enveloping  material,  including  some  vegetable  mucilage 44.382 

99.109    "      " 

Other  substances  and  loss 891  includ- 
ing free  acetic  acid,  some  acetate,  sulphate,  and  muriate  of  potash,  phosphate 
and  sulphate  of  lime,  phosphate  of  magnesia  and  silica. 


19 

16 

16.5 

16.5 

17 


LINSEED:   ANALYSES  OF.  217 

Analyses  of  linseed  by  Meurein  (Journal  of  Pharmacy  [3],  XX,  96) : 

Gum  and  soluble  salts 14  per  cent  -^ 

Soft  resin  and  fixed  oil 1    "  "  I  Episperm. 

Matter  insoluble  in  water  but  soluble  in  ether.  .  .  .  4    "  "  f  21  percent. 

Water 2    "  "  J 

Soft  resin  and  fixed  oil 6    "  "  -, 

Matter  insoluble  in  water  but  soluble  in  ether.  ...  12    "  "  I  Endosperm. 

Matter  soluble  in  water 3    "  "  j  23  per  cent. 

Water 2    "  "  J 

Fixed  oil 30    "  "  •> 

Matter  insoluble  in  water  but  soluble  in  ether.  ...  18    "  "  I 

Matter  soluble  in  water 3    "  "  [  56  Percent- 

Water..  5    "  "  J 


100  per  cent. 

Analyses  by  Anderson:* 
Albuminous  substances. 24 . 44  per  cent 


Gum  and  cellulose 30.73  ' 

Oil 34.00  "  " 

Ash 3.33  "  " 

Water..  7.50  "  " 


100  per  cent. 


Way's  analyses  of  33  samples  of  linseed  from  various  countries : 

Nitrogen 3.3    to     5 . 28  per  cent. 

Fat. 34.70  "  38.42    "      " 

Ash 2.68"      5.64"      " 

Water 8.51"  12.33    "      " 

Way's  analyses,  ditto  of  the  oil-cake  from  above  samples: 

Nitrogen 3 . 92  to  5 . 25  per  cent. 

Fat 6.60  "  15.32    "      " 

Ash 5.45  "  22.66    "      " 

Water 6.56  "  10.26    "      " 

Albuminous  substances.  .  .  25.00  "  36.00    "      " 


The  general  composition  of  all  siccative  oils  is: 

Carbon 77 . 40  to  76 . 00  per  cenU 

Hydrogen 11. 30  "11. 10    "      "      fKonig. 

Oxygen 12.70  "  11.50    "      "     J 

Linseed  f  also  contains  a  large  quantity  of  mucilage  deposited  in 
the  outer  layers  of  cells  of  the  epidermis,  which  swells  up  on  macerating 

*  "  Analyses  of  Linseed."    Highland  Agricultural  Society  Journal  (New  Series), 
Number  69,  p.  376. 

t  Schmidt.     Amer.  Chem.  Phar.,  II,  26. 


218  LINSEED-OIL:   ANALYSES  OF. 

the  seed  with  water,  sufficient  to  burst  the  cells.  One  part  of  linseed 
boiled  in  16  parts  of  water  yields  mucilage  enough  to  be  drawn  out 
into  threads,  and  forms  a  dark-colored  spongy  mass  when  dry.  This 
crude  mucilage  contains  in  addition  to  the  true  vegetable  mucilage, 
legumin,  albumin,  and  an  organic  acid,  probably  malic  acid;  also 
ash  constituents,  chiefly  lime,  potash,  and  iron,  partly  as  phosphates, 
and  partly  united  in  the  ash  by  carbonic  acid.  Linseed  mucilage 
precipitated  by  alcohol  gives  11  per  cent  of  ash  containing  4  per  cent  of 
carbonic  acid. 

Linseed-oil  has  a  specific  gravity  of  0.928  to  0.953,  or  7.743  to 
7.952  pounds  per  United  States  gallon.  The  oil  from  an  average 
quality  of  ripe  seed  extracted  by  various  processes  contains: 

Cold  Process.  Hot  Process. 

Carbon 75 . 17  per  cent.  Carbon 78 . 1 1  per  cent. 

Hydrogen 10.98    "      "  Hydrogen 10.96    "      " 

Oxygen 13.85    "      "  Oxygen... 10.93    "      " 


100.00   "  100.00    ' 

The  carbon-disulphide  process  gives  more  oxygen  and  less  carbon. 
The  oil  extracted  by  the  naphtha  and  percolating  process  does  not 
show  any  material  difference  in  the  quantity  of  the  oil,  but  is  thought 
to  give  a  quicker  drying  oil  than  by  the  old  or  cold-drawn  process. 
But,  however,  it  leaves  some  of  the  glucerides  of  the  oil  in  the  oil-cake 
as  well  as  some  of  the  albumin. 

The  glucerine  in  the  oil  in  the  form  of  gluceride  or  other  ethers  is 
needed  in  the  change  of  the  fatty  acids  to  form  the  soap  compounds 
that  give  the  binding  quality  to  the  oil.  The  albuminous  substances 
are  organic  and  are  subject  to  decomposition,  and  constitute  "the 
drops"  or  "mucosities"  that  the  boiling  process  removes,  or  if  the 
oil  is  used  in  its  raw  state,  the  driers  added  are  intended  to  affect  them 
so  that  they  may  be  oxidized  and  dried. 

Unripe  linseed  or  the  seed  from  flax  raised  for  the  fibre  (the  condi- 
tion that  furnishes  a  large  part  of  the  commercial  linseed-oil)  contains 
5  to  8  per  cent  of  water. 

The  yield  of  oil  from  the  different  classes  (red,  blue,  or  white  flower) 
of  linseed  varies  from  20  to  33  per  cent  of  the  weight  of  the  dry  seed. 
The  classification  of  American  linseed,  in  regard  to  its  quality,  is 
established  by  the  Board  of  Trade  of  the  city  of  Chicago,  as  follows: 

No.  1.  The  minimum  weight  per  bushel  shall  be  51  pounds,  the 


LINSEED-OIL:   QUALITIES  OF.  219 

maximum  quantity  of  field-stock,  storage,  or  other  damaged  seed 
not  to  exceed  12J  per  cent. 

No.  2.  The  weight  per  bushel  shall  be  50  pounds,  the  damaged 
seed  not  to  exceed  25  per  cent. 

No.  3.  The  weight  to  be  not  less  than  46  J  pounds  per  bushel; 
the  damaged  seed,  not  to  be  in  excess  of  20  per  cent,  is  graded  "  Re- 
jected." 

No.  4.  No  grade.  Seed  comprises  all  damp,  mouldy,  warm  seed 
or  those  in  a  heated  condition  and  unfit  for  temporary  storage.  All 
seed  that  is  burnt,  smoky,  or  intermixed  with  burnt  seed  is  posted 
as  "  Burnt  or  Smoky  Flaxseed." 

All  sales  of  flaxseed  are  made  upon  the  basis  of  pure  seed;  that  is, 
seed  tendered  for  contract  deliveries  may  carry  impure,  damaged,  or 
foreign  seed  matter,  but  must  contain  the  sale-quantity  of  pure  seed  as 
given,  and  for  such  pure  seed  only  shall  payment  be  required. 

Linseed  yields  by  the 

Cold  process  of  extraction,  about  20  per  cent  of  oil. 
Hot  process  "  "  "     27     "      "     "    " 

Carbon-disulphide  process,       "     33     "     "     "    " 

Or  from  15  to  18  pounds  of  oil  per  bushel  of  No.  1  commercial  linseed 
by  the  most  improved  processes  of  extraction. 

The  average  results  in  oil  of  a  number  of  samples  of  the  following 
substances,  extracted  by  filtration  in  100  parts,  are  as  follows: 

Linseed 27 . 15  per  cent.  Walnuts. 50 . 06  per  cent. 

Hemp-seed 25.87    "      "  Almonds 52.41    "      " 

Poppy-seed 49 . 40    "      "  Grape  seeds 17 . 95    "      " 

Linseed-oil  corresponds  to  the  formula  (Mulder)  C16H2502  or 
C^H-^Ojj.  It  is  an  hydride  of  linoleic  acid  (C16H26O2).  Specific  gravity, 
0.9266.  Linoleic  acid  is  a  faint-yellow,  limpid  oil,  insoluble  in  water, 
and  does  not  solidify  at  18°  F.,  and  has  both  the  nature  of  an  oil  and 
a  resin.  It  decreases  continually  in  weight  for  90  days,  losing  from 
5  to  8  per  cent. 

Linoleic  acid  is  peculiar  to  all  siccative  or  natural-drying  oils, 
and  when  fully  oxidized  by  exposure  to  the  air,  forms  oxylinoleic 
acid  (C32H54O5)  or  linoxyn  (Mulder). 

Hazura  and  Bower  (Monatsch.,  Vol.  I,  p.  459)  found  that  the  rate 
of  oxidation  and  consequent  hardening  of  linseed  and  other  siccative 
oils  depended  upon  the  ratio  of  linoleic  and  linolenic  acids  present. 


220  LIN  SEED-OIL:   QUALITIES  OF. 

The  linoxyn  formed  is  insoluble  in  water,  dilute  acids,  alcohol,  or 
ether,  and  is  heavier  than  water. 

Hazura  describes  linseed-oil  as  formed  of  linolic,  linoleic,  and 
iso-linolenic  acids,  and  that  a  high  proportion  of  the  two  latter  acids 
is  characteristic  of  this  oil. 

Linseed-oil  is  composed  of  drying  oil,  80  parts,  and  non-drying  or 
fatty  oils,  20  parts.  Of  the  latter,  8  parts  are  glycerine  ether,  the 
volatile  element  of  the  oil,  that  in  the  chemical  changes  among  the 
oil  acids  by  the  absorption  of  oxygen  in  the  process  of  drying,  is 
absorbed  or  lost  in  the  change  to  linoleic  acid,  with  a  direct  loss  in 
weight  of  the  new  oil  compound. 

The  fatty  acids  in  linseed-oil  are: 

Margaric  acid C17H,4O2;  specific  gravity  0 .810 

Palmitic  or  benic  acid C16H32O3         "  "       0 . 809 

Oleic  acid C1(,H34O2         "  "       0.808 

Stearic  acid C^H^O,         "  "        0.805 

Margaric  acid  is  considered  simply  as  a  mixture  of  stearic  and 
palmitic  or  benic  acid  of  identical  composition  (C18H3402). 

The  composition  and  specific  gravities  of  all  the  fatty  oils  vary 
but  little,  and  the  influences  that  affect  one  affect  all. 

Oleic  ether  (€20113202),  specific  gravity,  0.807,  associated  with  the 
fatty  acids,  dissolves  all  solid  fats,  stearic,  palmitic  acids,  etc. 

The  glycerides  or  glycerine  ethers  have  the  characteristics  of 
ethylin  (C3H1202) ;  they  are  the  most  volatile  of  the  group,  and  form  a 
component  part  of  the  fatty  elements  in  all  siccative  oils.  The  heavy 
odor  recognized  when  a  burning  tallow  candle  is  blown  out  is  due 
to  the  glycerine  ether  that  comes  from  the  smoldering  wick.  A 
heat  of  170°  F.  is  adequate  to  dispel  or  to  cause  an  absorption  of  the 
glycerides  into  the  fatty  acids  in  the  oil  to  form  the  insoluble  soap  com- 
pound. The  albuminous  substances  in  the  oil  coagulate  at  about 
160°F.,  and  in  the  steamed  or  hot  process  of  extracting  linseed-oil, 
the  meal  is  cooked  at  190°  to  200°  F.  to  prevent  the  albumin  from 
flowing  out  when  pressed. 

These  changes  indicate  the  merits  of  a  low  and  long-continued 
heat  in  the  process  of  boiling  oil,  instead  of  the  quicker  and  more 
energetic  changes  due  to  higher  temperature  of  the  oil,  and  will  be 
referred  to  hereafter. 

The  siccative  oils  of  commercial  importance  are  20  in  number, 
the  principal  of  which  are  linseed,  poppy,  hemp,  walnut,  sunflower, 


SICCATIVE  AND  NON-DRYING  OILS. 


221 


grape,  Scotch  and  silver  fir,  and  spruce.  The  specific  gravities  of 
the  whole  number  (20)  range  from  0.9202  to  0.9358,  varying  so  little 
that  the  hydrometer-test  is  of  little  moment  to  determine  their  char- 
acter. The  vegetable  non-siccative  oils  of  commercial  importance 


Fie.  27. -Common 
luttatiVuimura),  a.  seed,  mitt 
nifled  0  times :  6,  longitudinal 
section,  showing  embryo  im- 
bedded in  the  endosperm. 


Fie.  in-Cotton  iCo*.,!,,-™ 


n,  wed.  dolinuxl.  nmsnificd  3  time*:  t.  «eed  with 
sertlon.  showing  the  crumpled  embryo  filling  the  seed  owte 


CQTTON-SEED  OIL. 


Flc.31-8esame(Sf«am»m<nd<nim).  o.seed. 
magnified  10 times:  4, transverse section. 


no.  ». -Castor-oil  boan  (Kirin*.  I..-.—.-,. 
04  fruit,  maguinedlj  times;  6.  «ewl.  front, 
magnified  2;  times ;  c.  back :  d.  longitudinal 


FIG.  34.— Oil-seeds.     (Enlarged.) 


are  76  in  number,  the  principal  ones  being  the  castor  (specific  gravity, 
0.964),  olive,  cottonseed  (specific  gravity,  0.9306,  almost  identical 
with  linseed),  resin,  almond,  beechnut,  horse-chestnut,  hazelnut, 
peanut,  croton,  sesame,  colza,  rape,  mustard,  with  specific  gravities 
ranging  from  0.913  to  0.942.  They  mix  thoroughly  with  each  other 
and  with  the  siccative  oils,  and  the  specific  gravity  of  a  pure  linseed- 
oil  can  be  easily  counterfeited,  even  if  its  quality  cannot  be.  Vege- 


222     COMPOSITION  OF  SICCATIVE  AND  NON-DRYING  OILS. 


table  oils  additional  to  the  above,  used  medicinally  and  for  soap, 
burning,  and  food,  are  85  in  number. 

Vegetable  oils,  volatile  and  essential,  number  134,  or  a  total  of 
315  non-drying  oils  available  for  the  purpose  of  adulteration.  Add 
80  animal  and  fish  oils  to  the  above,  and  it  may  be  conjectured,  the 
source  from  which  a  yearly  supply  from  the  whole  world  of  250,000,000 
gallons  of  linseed-oil  and  other  siccative  oils  can  supply  a  demand 
for  about  350,000,000  gallons  of  paints,  varnishes,  japans,  and  other 
uses,  including  the  wastes  of  manufacture. 

As  before  stated,  if  the  flax  is  raised  for  the  fibre,  the  seeds  do  not 
mature  at  the  same  time,  hence  they  furnish  a  thin  watery  oil  with  a 
greater  quantity  of  the  albuminous  substances,  gum,  sugar,  and  cellu- 
lose, called  "  mucosities,"  than  the  54.44  per  cent  to  58.50  per  cent 
found  in  ripe  seed.  Unripe  or  mildewed  linseed  is  no  more  capable 
of  furnishing  a  good  oil  than  a  green  apple  will  make  either  good 
cider  or  good  vinegar;  an  unripe  grape,  good  wine;  or  grain  or  corn 
harvested  in  the  milk  will  make  good  bread ;  and  no  amount  of  juggling 
in  the  subsequent  manipulations  of  the  paint  manufacturer  can 
replace  the  simple  operations  of  nature,  or  ripen  her  unripe  products 
or  produce  them  from  synthetical  compounds. 

The  following  is  a  comparison  of  the  composition  of  a  few  of  the 
principal  oil-seeds: 

SICCATIVE  OILS. 


Oil. 

Specific 
Gravity. 

Carbon. 

Hydrogen. 

Oxygen. 

Linseed  

0.9352 
0.9270 
0.9285 
0.9307 

0.9288 

77.40 
76.57 
77.20 
76.00 
1  76.65 
177.15 

11.10 
11.41 
11.31 
11.30 
11.46 
11.73 

11.50 
12.02 
11.49 
12.70 
11.89 
11.12 

Poppy-seed,  (black) 

"         "     (white)   . 

Hemp-seed  

Walnut  

VEGETABLE  NON-DRYING  OILS. 


Cottonseed  

0  9306 

76  40 

11  53 

12  27 

0.9155  ) 

"     (summer)           .            . 

0  9165  ) 

78.04 

12.04 

9.92 

Earthnut  or  Peanut   

0  918 

75  73 

11  57 

12  70 

Beechnut.  .  .         

0  923 

76  65 

11  47 

11  89 

0.9639 

77  21 

13  36 

9  43 

COMPOSITION  OF  NON-SICCATIVE  AND  NON-DRYING  OILS.   223 


The  grains  yield  oil  similar  in  character  to  the  other  non-drying 
oils,  viz.: 


Specific 
Gravity. 

Carbon. 

Hydrogen. 

Oxygen. 

Hye 

76  71 

11  79 

11   50 

Wheat 

77  19 

11  97 

10  84 

Barley  and  oats  .  .                 .... 

...j 

77.50 

11.96 

12.78 

Maize  and  lupine  

i 

to 

to 

to 

Peas  and  beans  

( 

75.67 
77.40 

11.43 
11  30 

10.69 
12  70 

Potatoes  and  rice  

to 

to 

to 

Beets,  etc  

76.00 

11.15 

11  50 

The  increase  in  oxygen  in  the  grain  oils  is  at  the  expense  of  the  carbon. 
MISCELLANEOUS  NON-DRYING  OILS  AND  SUBSTANCES. 


0.945 

78.90 

10.97 

10  13 

(0.984    ) 
1      to      V 

79.27 

10.15 

10  58 

Beef  tallow 

(0.9910  ) 
0  938 

79  00 

11  70 

9  30 

Beeswax 

81  60 

13  90 

4  50 

Spermaceti 

81.60 

12  80 

5  60 

The  vegetable  aromatic  volatile  oils  from  lemons,  oranges,  cloves, 
cinnamon,  etc.,  are  of  the  same  chemical  composition:  Carbon,  88.25; 
hydrogen,  11.75.  When  they  oxidize,  it  is  at  the  expense  of  the 
carbon  element.  The  diversities  in  their  odor  are  due  to  a  different 
arrangement  of  their  atoms. 

Poppy-seed  furnishes  a  cold-pressed  siccative  oil  of  excellent 
quality.  Being  an  imported  article  its  price  prevents  its  use  except 
in  the  finer  color  paints.  The  exceptionally  good  results  attendant  on 
the  use  of  French  zinc  oxide  are  principally  due  to  the  use  of  this  oil. 
It  dries  slower  than  linseed-oil  and  faster  than  walnut-oil.  It  does 
not  remain  sticky  so  long  as  linseed-oil,  not  being  so  fatty,  and  takes 
up  less  oxygen.  It  is  used  for  the  finer  classes  of  varnishes.  It  con- 
tains 20  per  cent  of  non-drying  and  80  per  cent  of  drying  oil.  Linseed- 
oil  clarified  by  sulphuric  acid  has  generally  taken  the  place  of  poppy- 
oil.  Walnut-oil  contains  30  per  cent  of  non-drying  and  70  per  cent 
of  drying  oil.  The  cold-process  oil  is  light  colored  with  a  pleasant 
smell  and  taste;  after  a  short  exposure  to  the  sunlight  it  becomes 
as  clear  as  water.  The  hot-process  oil  is  characterized  by  a  deep  color 
and  unpleasant  odor;  it  has  more  mucilage  in  it,  and  does  not  dry 
as  well  as  the  cold  pressed. 


224  SPECIFIC   GRAVITY  OF  OILS. 

SPECIFIC  GRAVITIES  OP  OILS  AND  FATS, 

Poppy-seed  oil 0.9245 

Raw  linseed  cold-drawn  oil 0 . 9299  to  0 . 932 

Boiled  linseed-oil 0.9400  "  0.942 

Crude  cottonseed-oil 0 . 9224 

Refined  yellow  ditto 0 .9230 

Water-white  ditto, 0 .9288 

Menhaden-oil  (dark) 0 . 9292 

"  (light) 0.9325 

Tanner's  cod-oil 0.9205 

Porgy-oil 0 . 9332 

Resin,  commercial  yellow 1 . 0700 

Resin-oil,  first  run 0 .9835 

"  "  third  run 0.9887 

"  "  other  runs 0.9910  to  0.960 

Crude  Lima  petroleum 0 . 839    =  7  pounds  per  gal. 

Lard-oil 0.915 

Whale-  or  train-oil 0 . 925 

Sperm-oil 0.943 

Porpoise-oil 0.937 

Beef  tallow 0.927 

Mutton  tallow. .  .0.938 


CHAPTER  XXIII. 

BOILING   LINSEED-OIL. 

J.  Nelson  Neil's  Experiments. 

THE  study  of  the  composition  and  properties  of  the  siccative  oils 
has  been  but  little  advanced  since  Mr.  J.  Nelson  Neil  was  awarded  the 
Isis  Gold  Medal  of  the  Society  of  Arts  in  1832  for  a  paper  read  before 
that  society  on  "Oil  Boiling  and  Varnish  Making"  (published  in  the 
Transactions  of  the  Society,  Vol.  XLIX,  Part  II),  which  treats  so 
exhaustively  upon  the  modes  of  manipulation,  recipes,  and  precau- 
tions to  be  used,  that  the  paper  is  the  foundation  for  all  subsequent 
accounts  and  modes  of  manufacturing  varnishes.  The  additions 
and  modifications  which  have  been  worked  out  since  that  time  have 
not  materially  altered  the  processes  of  Mr.  Neil,  either  in  the  better- 
ment of  the  quality  of  the  varnish  or  the  oil  product,  but  relate  more 
particularly  to  a  shorter  time  and  possibly  less  cost  of  manufacture 
than  given  by  him,  which  comprised  the  application  of  direct  fire  to 
the  kettles  instead  of  the  steam-jacket  kettles  and  devices  used  by 
later  experimenters  and  manufacturers. 

The  substances  that  act  catalytically  part  with  some  of  their 
oxygen  in  the  oil,  and  become  to  a  certain  extent  deoxidized,  and 
again  coming  into  contact  with  the  air  either  mechanically  blown 
through  the  combined  mass  of  oil  and  driers,  or  by  surface  exposure 
in  the  settling-tank  or  barrel,  recover  their  primal  condition,  and  are 
ready  to  do  the  same  work  over  again.  It  is  the  necessity  for  the 
reoxidation  of  the  driers  that  causes  the  general  adoption  of  the  air 
agitation  and  steam  processes  now  in  general  use  for  the  boiling  of 
oil  and  manufacture  of  varnishes,  etc.  These  driers,  without  becom- 
ing materially  altered,  induce  an  alteration  in  the  linseed-oil  sub- 
jected to  their  operation.  We  may  imagine  this  action  as  similar 
to  that  by  which  spongy  platinum  explodes  a  mixture  of  oxygen  and 
hydrogen,  or  a  platinum  wire  is  kept  red  hot  by  the  vapor  of  ether. 

225 


226  BOILING  LINSEED-OIL. 

In  properly  prepared  varnishes  and  paints  from  pure  linseed-oil, 
the  gain  in  weight  after  thoroughly  dry  is  from  8  to  10  per  cent  of 
the  vehicle,  and  it  is  heavier  than  water.  Any  paint  that  does  not  show 
a  marked  increase  in  weight  in  drying  can  be  set  down  as  one  of  the 
hundreds  of  bastard  compounds  that  masquerade  under  the  guise  of 
paint,  with  more  resin,  fish-oil,  and  hydrocarbon  substances  in  its 
vehicle  than  linseed  or  other  siccative  oils. 

M.  E.  Chevreul's  Experiments. 

These  experiments  of  Mr.  Neil  were  followed  by  the  experiments 
of  Mr.  M.  E.  Chevreul,  who  contributed  a  paper  in  1856  to  the  Annales 
de  Chime,  corroborating  Mr.  Neil's  deductions  upon  the  drying  of 
siccative  oils,  and  by  him  clearly  laid  down,  viz. : 

First.  That  it  is  the  absorption  of  oxygen  by  the  siccative  oils 
and  the  change  of  the  oleic,  margaric,  and  stearic  acids  of  which  they 
are  composed,  and  the  chemical  combination  with  each  other  in  the 
presence  of  oxygen  into  the  linoleic  and  linolenic  acids,  that  is  the 
cause  of  their  solidification,  which  term  he  thinks  more  clearly  defines 
the  action  of  the  oil  than  drying,  which  in  general  may  mean  evapora- 
tion, which  is  a  term  adaptable  to  all  liquid  bodies,  or  rather  indi- 
cates the  removal  of  liquid  from  all  bodies.  This  definition  appears 
to  be  apropos  to  many  of  the  latter-day  cheap  mixtures  called  paints ; 
the  difficulty  experienced  with  some  of  which  is  not  to  have  them 
dry  in  a  reasonable  time,  but  to  have  them  keep  liquid  long  enough 
to  spread  them  at  all. 

Second.  That  the  oxidation  of  the  oil  is  a  chemical  process  and 
naturally  inherent  in  itself.  The  action  of  heat,  as  in  boiling,  hastens 
the  drying  or  resinification  of  the  oil  by  removing  the  water  and 
mucosities.  That  all  substances  which  can  be  used  as  driers  must 
be  such  as  are  capable  of  parting  with  oxygen  or  dissolving  in  it;  and 
being  of  themselves  oxidizable  in  combination,  they  in  that  way 
increase  its  absorptive  power.  There  is  a  class  of  driers  (white  cop- 
peras, for  instance)  which  act  catalytically,  while  mechanically  sus- 
pended or  in  contact  with  the  oil,  and  increase  its  oxygen  absorptive 
power  by  their  presence,  but  leave  no  increase  of  drying  power  when 
withdrawn. 

Third.  That  manganese  and  litharge  were  the  most  powerful 
driers,  and  when  used  in  excess  and  settled  from  the  oil,  they  acted 
with  greater  power  when  used  a  second  time. 


BOILING  LINSEED-OIL.  227 

Linseed-oil  boiled  5  hours  without  drier,  required  38  days  to  become 
thoroughly  hard.  When  boiled  the  same  period  with  new  peroxide 
of  manganese,  it  dried  in  2  days.  When  boiled  6  hours  with  peroxide 
of  manganese  that  had  been  used  many  times  before,  it  required 
one-half  day  to  dry  firm  and  hard. 

Fourth.  That  manganese  driers  for  exposed  paints  appear  to  be 
less  durable  than  red  lead  or  litharge  driers.  They  harden  quicker 
and  become  more  brittle,  from  the  harder  character  of  the  soap  they 
contain,  which  is  further  developed  in  hardness  by  the  heat  of  the  sun. 

Fifth.  The  manganese-drier  paints  appear  to  peel  more  readily 
than  red-lead  driers,  especially  upon  ironwork  that  has  but  few 
points  or  irregularities  of  the  surface  to  which  the  paint  can  adhere. 
Hence  such  a  paint  for  an  iron  surface  must  remain  in  a  measure 
softer  and  more  elastic,  or  else  it  will  be  thrown  off  or  peel  by  the 
changes  in  temperature  and  the  expansion  and  contraction  of  the 
metal. 

Peroxide  of  manganese  is  electro-negative  to  iron  and  steel,  and 
is  noted  for  the  freedom  with  which  it  imparts  its  oxygen  to  these 
metals.  It  is  used  in  the  manufacture  of  steel  as  a  purge  to  burn 
out  the  impurities  in  it. 

ANALYSIS  OF  DIOXIDE  OF  MANGANESE  OR  PYROLTJSITE  (MnO). 
Red  oxide  of  manganese 84 . 05  to  87 . 00  per  cent. 


Oxygen 14.58 

Sesquioxide  of  iron 1 . 30 

Alumina 0 . 30 

Baryta 0 . 67 

Calcium traces 

Silica 0.80 

Water..  5.80 


11.45 
0.40 
0.00 
1.20 
0.00 
0.51 
1.92 


Sixth.  That  linseed-oil  heated  until  it  lost  one-sixth  of  its  weight 
became  thicker,  unctuous,  and  viscid,  and  dried  more  readily,  forming 
a  tough,  crude,  turpentine-like  mass,  scarcely  soluble  in  any  other  oil 
(printer's  varnish).  When  linseed-oil  is  heated  to  325°  to  375°  F. 
it  will  take  fire  and  continue  to  burn  without  any  further  application  of 
heat  from  without,  until  only  tar  or  charcoal  remains. 

Nut-  and  poppy-seed  oils  also  possess  this  feature,  which  is  some- 
times employed  as  a  test  of  the  purity  of  these  oils.  If  these  oils 
are  adulterated  to  any  great  extent  with  fish,  resin,  or  mineral  oils, 
they  will  not  continue  to  burn  after  ignition  without  a  further  addi- 
tion of  heat. 


228  BOILING  LINSEED-OIL. 

Prof.  ChevreuPs  experiments  to  show  the  effects  of  atmospheric 
gases  on  the  drying  of  linseed-oil  were  as  follows: 

Four  panels  of  wood  were  painted  on  one  side  with  white  lead 
and  on  the  other  side  with  zinc  oxide,  the  vehicle  being  raw  linseed-oil. 

4:      No.  1  was  placed  in  a  closed  glass  vessel  exposed  to  carbonic-acid  gas. 
No.  2  was  placed  in  a  similar  vessel  exposed  to  confined  air. 
No.  3     "        "         "         "          "  "        "  free  air. 

No.  4     "        "         "         "          "  "        "oxygen  gas. 

The  results  were  as  follows : 

After  24  Hours.  After  72  Hours. 

_r  i  The  white  lead  nearly  set.  Set  but  without  adhesion  to 

No.  1.  Carbonic-      \ 

the  wood. 

(  The  zinc  oxide  still  fresh.  Absolutely  fresh. 

(  The  white  lead  nearlv  dry.  Perfectly  dry. 

No.  2.  Limited  air.  \  „,       .          .,       ,  ,",     J.   ,  it          -u 

\  The  zinc  oxide  set  but  not  dry. 

.          j  The  white  lead  nearly  dry.  "  " 

iir*       \  The  zinc  oxide  set  but  not  dry.          "          " 

No.  4.  Oxygen  gas.    Both  perfectly  dry.  "  " 

Professor  Vincent's  Experiments. 

Prof.  Chas.  W.  Vincent's  experiments  in  1859  were  upon  the  line 
of  boiling  oil  without  the  presence  of  driers,  and  that  a  high  tem- 
perature was  not  necessary.  The  temperature  used  by  Mr.  Vincent 
was  that  due  to  steam  at  40  pounds  per  square  inch,  267°  F.,  used  in  a 
steam- jacketed  kettle  in  connection  with  mechanical  agitation  by 
revolving  blades  and  a  current  of  compressed  air  moderately  heated 
by  the  act  of  compression.  This  process  is  that  in  general  use  at 
present  in  the  manufacture  of  linoleum,  and  it  is  believed  that  the 
Germans  practised  this  method  many  years  preceding  1859.  Pro- 
fessor Vincent's  conclusions,  drawn  from  experiment,  were  that  air 
blown  through  the  mass  of  heated  oil  is  not  as  important  a  part  of  the 
process  as  many  have  assigned  to  it,  and  in  reality  effects  nothing 
toward  making  the  oil  a  drying  one.  He  boiled  linseed-oil  with  air 
alone,  but  without  driers,  for  three  days  consecutively,  keeping  up  a 
high  temperature  the  whole  time,  and  the  resultant  boiled  oil  re- 
quired precisely  the  same  time  to  dry  as  the  raw  oil  from  which  it 
was  prepared.  The  body,  however,  had  become  so  much  increased 
that  its  consistency  was  more  that  of  a  varnish  than  an  oil.  In  the 
oil  subjected  to  the  heat  alone  for  the  same  time,  without  any  air, 
except  such  as  came  to  it  in  contact  with  its  surface  in  the  kettle, 


BOILING  LINSEED-OIL.  229 

there  was  no  such  increase  in  its  consistency  as  in  the  former  case; 
the  oil  simply  became  more  greasy,  had  less  difficulty  in  penetrating 
the  capillary  tubes  of  paper,  plaster,  etc.,  than  it  previously  had,  and 
had  decidedly  less  drying  power.  The  oil  that  had  been  boiled  with 
the  air-blast  was  less  greasy  and  had  a  greater  consistency.  Briefly, 
the  surface  exposure  to  the  air  and  the  heat  secured  a  sufficient  amount 
of  body.  The  driers  produced  any  required  shade  of  color  in  the  oil 
and  reduced  the  time  of  drying  from  3  and  4  days,  for  the  raw  oil, 
to  6  hours  in  the  summer  and  8  hours  in  the  winter  for  the  boiled. 
Boiled  oil  that  is  subject  to  long  voyages  at  sea  is  apt  to  become  fatty 
and  not  free  working.  This  is  due  to  the  agitation  it  gets  from  the 
motion  of  the  ship  while  it  is  under  the  increase  of  temperature  due 
to  the  hold  or  cargo  space  in  the  ship,  being,  in  fact,  a  long-continued 
low-temperature  and  agitation  process  of  boiling.  The  manufacturer 
guards  against  this  result  by  adding  to  boiled  oil  for  shipment  by 
sea,  about  one-fourth  its  volume  of  raw  oil,  the  oil  becoming  brighter 
in  consequence  of  the  addition.  Professor  Vincent's  steam-kettle 
process  of  boiling  gives  an  oil  of  a  lighter  shade  than  the  direct  fire 
or  high-temperature  process.  In  both  processes,  acrylic  acid  (C3H4O2), 
a  monobasic  acid,  is  produced  by  the  oxidation  of  acrolein.  Acrylic 
or  acroleic  acid  when  purified,  is  a  colorless  liquid  of  a  slightly  empy- 
reumatic  odor,  lighter  than  water  and  mixable  with  it  in  all  propor- 
tions. 

Acrolein  (C3H4O)  is  the  acid  principle  produced  by  the  destruc- 
tive distillation  of  fatty  bodies,  resulting  from  the  decomposition 
of  glycerine  (C3H8O3).  Acrolein  is  a  colorless,  limpid,  strongly 
refracting  liquid,  lighter  than  water,  boils  at  126°  F. ;  vapor  density, 
1.897.  Its  vapor  is  so  intensely  irritating  that  a  few  drops  diffused 
in  a  room  are  sufficient  to  render  the  atmosphere  unsupportable. 
It  burns  with  a  clear  bright  flame,  and  dissolves  in  40  parts  of  water 
and  readily  in  ether.  The  solutions  at  first  are  neutral,  but  gradu- 
ally oxidize  and  turn  acid  in  contact  with  the  air.  Under  water  it 
changes  into  a  resinous  substance  (disacryl-resin)  and  the  water 
becomes  charged  with  aery  lie,  formic,  and  acetic  acids.  The  vapor  of 
acrolein  passed  through  a  red-hot  tube  is  decomposed  with  the  formation 
of  water  and  charcoal.  Its  vapor  is  highly  corrosive  to  iron  bodies. 

Acrolein  is  developed  by  the  decomposition  of  the  mucosities 
in  the  raw  linseed-oil  under  the  influence  of  the  boiling  heat,  and 
indicates  the  slower  decomposition  of  these  substances  in  a  raw-oil 


230  BOILING  LINSEED-OIL. 

vehicle  for  a  paint.  The  slower  process  of  solidification  of  the  raw 
oil  enclosing  them,  as  it  were,  in  a  film  of  the  vehicle,  to  develop  later 
by  decomposition  into  a  destructive  agent  of  the  paint.  The  pig- 
ments in  the  paint  may  delay  this  decomposing  action  for  a  time, 
but  cannot  wholly  prevent  it,  and  in  many  cases  hasten  it.  The 
removal  or  destructive  change  of  these  mucosities  is  absolutely  neces- 
sary in  baking  japans,  varnishes,  japan  driers,  and  linoleum;  and  if 
found  detrimental  there,  it  must  necessarily  follow  that  they  are 
equally  so  in  a  paint  oil.  The  decomposing  point  in  a  pure  linseed- 
oil  made  from  thoroughly  ripe  linseed  is  nearly  100°  F.  higher  than 
in  an  oil  made  from  green  or  damaged  linseed. 

Professor  Sacc's  Experiments. 

Professor  Sacc's  experiments  in  brief  were,  2500  grains  of  oil 
boiled  for  10  minutes  only,  with  30  grains  each  of  litharge  and  red 
lead,  and  weighed  after  24  hours'  exposure  to  the  atmosphere,  the 
oil  had  lost  only  60  grains.  This  sample  increased  20  per  cent  in 
weight  after  complete  resinification.  A  second  sample  boiled  until 
there  was  a  loss  of  5  per  cent  in  weight  of  the  oil,  the  product  assumed 
a  molasses  consistency,  and  did  not  resinify  after  15  days'  exposure 
to  the  atmosphere.  A  third  sample  boiled  to  a  loss  of  12  per  cent 
became  a  caoutchouc-like  mass  that  the  atmosphere  had  no  effect 
upon  whatever.  It  was  insoluble  in  alcohol,  ether,  chloroform,  and 
bisulphide  of  carbon;  boiling  naphtha  only  dissolved  traces  of  it. 
The  only  action  which  dilute  acids  had  upon  it  was  to  extract  a  small 
quantity  of  the  oxide  of  lead  due  to  the  driers.  Hydrochloric  acid 
dissolved  it  slowly,  while  concentrated  sulphuric  and  nitric  acid 
dissolved  it  rapidly,  as  they  do  all  vegetable  and  animal  oils  and  tis- 
sues. This  substance  was  in  fact  identical  with  the  product  obtained 
by  the  modern  process  of  boiling  oil  for  the  manufacture  of  linoleum. 

Linseed-oil  submitted  to  a  dry  distillation  (without  boiling)  gave 
off  a  white  vapor  (acrolic)  from  which  was  condensed  a  colorless  oil 
(acrolic  acid),  having  the  odor  of  fresh  bread,  then  expanded  and 
yielded  a  distillate,  a  brown  empyreumatic  product;  finally,  a  mass 
resembling  jelly  and  caoutchouc  remained. 

The  Sulphuric-acid  Process. 

This  process  of  boiling  oil  has  been  adopted  by  a  number  of  manu- 
facturers. It  furnishes  an  oil  of  light  color  which  dries  well  and  rap- 


BOILING  LINSEED-OIL.  231 

idly,  mixes  with  all  pigments  without  leading  to  any  discoloration. 
Whites  retain  their  purity  of  tone  unchanged,  but  with  all  these  points 
in  its  favor,  the  process  cannot  be  recommended  for  the  preparation 
of  a  vehicle  to  be  used  for  a  ferric  protective  coating.  Briefly,  the 
oil  is  first  treated  with  a  dilute  sulphuric-acid  bath  (containing  about 
30  per  cent  of  sulphuric  acid)  which  is  agitated  with  the  oil  by  the  air- 
blast  to  dehydrate  it,  but  is  said  to  be  not  strong  enough  to  carbonize 
it.  After  standing  to  allow  the  oil  and  acid  to  separate,  the  oil  is 
run  off  into  the  usual  steam- jacketed  kettle  heated  to  about  267°  F., 
air  is  blown  through  the  mass,  while  a  solution  of  manganese  linoleate 
in  some  hydrocarbon  spirit  (probably  benzine)  is  added  gradually 
during  the  process  of  heating  and  blowing.  Cautionary  care  is  re- 
quired not  to  add  too  much  of  this  material.  It  is  the  writer's  opinion 
that  this  caution  should  extend  to  the  point  of  not  adding  any  manga- 
nese asociated  with  any  hydrocarbon  vehicle  to  the  oil,  and  that  pro- 
hibition should  extend  to  the  use  of  any  sulphuric,  nitric,  or  other 
caustic  acid  of  any  strength  to  the  oil  in  its  preliminary  stage.  It 
is  almost  impossible  to  clear  an  oil  of  either  high  or  low  specific  gravity, 
of  any  acid  of  whatever  strength  of  solution  to  which  it  may  be  ex- 
posed. More  or  less  of  the  clarifying  acid  will  be  held  in  the  oil  either 
free  or  in  combination  with  the  water  in  the  oil,  that  even  a  long 
washing  with  water,  aided  by  an  air-blast  agitation,  will  not  remove. 
Kerosene,  naphtha,  gasolene,  etc.,  are  purified  by  treating  with 
sulphuric  acid  and  then  thoroughly  washed  with  water  and  a  long 
agitation  by  the  air-blast,  and  are  then  often  found  to  contain  acid 
enough  to  perforate  the  tin  cases  in  which  they  are  shipped.  The 
slight  improvement  in  the  color  of  the  boiled  oil  by  this  process  is  a 
very  poor  recommendation  for  its  use.  The  same  results  are  obtaina- 
ble by  the  ordinary  steam-kettle  process,  using  well-known  mineral 
substances;  for  instance,  the  zinc  and  manganese  salts  will  remove 
or  throw  down  the  mucosities,  clear  the  oil  to  any  desired  shade,  and 
cause  it  to  dry  promptly,  while  the  water  in  the  oil  will  be  evaporated, 
naturally  by  the  heat,  and  the  dangers  of  the  sulphur  element  avoided. 

Thorp's  Experiments  with  Driers. 

The  action  of  various  mineral  and  metallic  driers  upon  linseed- 
oil  in  the  process  of  boiling  to  determine  their  effect  on  the  color  of 
the  oil  and  the  time  of  drying  were  made  by  Mr.  Frank  H.  Thorp,  S.B.* 

*  Journal  of  Chemical  Industry,  Volume  IX,  p.  628,  1890.  Reprinted  in 
the  Scientific  American  Supplement,  No.  757,  Volume  XXX,  June  5,  1890. 


232  BOILING  LINSEED-OIL. 

The  oil  experimented  upon  was  in  every  case  from  the  same  barrel, 
and  was  a  very  light-colored,  cold-pressed,  Calcutta  raw  linseed-oil, 
specific  gravity,  0.93.  The  weight  of  oil  under  test  was  in  each  case 
the  same,  50  c.c.  weighing  45.7  grms.  The  several  samples  were 
treated  in  glass  beakers  arranged  in  a  sand-bath  under  temperatures 
from  200°  to  300°  F.  In  general,  the  temperatures  from  230° 
to  275°  F.  gave  the  best  results.  The  time  of  actual  boiling  was 
from  1^  to  2^  hours,  and  the  percentages  of  driers  varied  from  less 
than  1  per  cent  to  2  per  cent  by  weight  of  the  oil  treated.  Litharge 
furnished  an  almost  colorless  oil  of  firm  film,  drying  in  from  6  to  10 
hours.  Lead  carbonate,  lead  acetate,  and  lead  borate,  each  furnished 
slightly  colored  oils  with  good  films,  drying  in  the  order  named,  in 
10,  12,  and  20  hours.  Red  lead,  lead  chloride,  and  lead  tartrate 
furnished  dark-colored  oils  of  good  films,  drying  in  from  20  to  24 
hours.  Red  lead  and  litharge,  2  per  cent  of  each,  also  the  other  lead 
salts  mentioned,  with  larger  percentages  than  two  of  each,  gave  dark- 
colored  oils,  all  with  firm  films,  drying  in  about  24  hours. 

Of  the  lead  driers,  litharge  gave  the  best  results  both  in  color, 
film,  and  drying  qualities.  Care  was  necessary  in  the  use  of  this 
drier,  to  not  overheat  the  oil,  thus  deepening  its  color.  The  zinc 
salts,  the  acetate,  borate,  citrate,  oxide,  and  sulphate,  furnished 
nearly  colorless  or  slightly  colored  oils  with  fairly  good  films,  but 
their  time  of  drying  was  from  36  to  46  hours.  Larger  amounts  of 
these  driers  than  2  per  cent  shortened  the  time  of  drying,  darkened 
the  color  of  the  oils,  and  they  did  not  clarify  satisfactorily. 

The  acetate  and  borate  are  the  best  of  the  zinc- salt  driers,  but 
none  of  them  act  catalytically  upon  the  oil  as  the  lead  and  manga- 
nese driers  do,  but  act  mechanically  or  only  while  present  (like  white 
copperas),  to  throw  down  some  of  the  mucosities,  but  do  not  cast 
them  all  out,  or  set  up  the  combination  changes  necessary  to  form 
the  linoleic  compounds  required  in  a  good  drying  oil.  The  manga- 
nese salts,  viz.:  the  acetate,  borate,  sulphate,  oxalate,  and  tartrate, 
all  gave  colorless  oils,  drying  with  good  firm  films  in  from  20  to  36 
and  40  hours.  The  citrate  and  formate  gave  slightly  darker-colored 
oils,  drying  in  about  24  hours  with  good  firm  films.  The  manganese 
borate  with  quantities  varying  from  1  to  3  per  cent  of  the  oil  and  with 
temperatures  of  220°  to  230°  F.,  gave  the  best  colored  and  drying  oils 
obtained  in  the  whole  line  of  experiments.  The  other  manganese 
salts  with  larger  than  1  per  cent  of  driers  with  temperatures  from 
250°  to  300°  F.,  gave  colored  oils  of  unsatisfactory  drying  power, 


BOILING  LINSEED-OIL.  233 

some  of  the  samples  being  tarred.  No  definite  conclusion  can  be 
drawn  from  Mr.  Thorp's  experiments  as  to  the  relation  between  the 
quantity  of  driers  dissolved  in  the  oil,  and  the  time  of  drying  of  the 
oil.  The  action  of  the  several  classes  of  driers,  as  well  as  the  various 
members  of  them,  was  erratic  and  the  drying  result  appeared  to  be 
governed  quite  as  much  by  the  temperature  of  the  bath,  time  of 
boiling,  and  agitation  of  the  oil  during  boiling,  as  by  the  chemical 
employed.  One  per  cent  by  weight  of  litharge  and  the  lead  driers, 
and  two-tenths  of  1  per  cent  of  the  manganese  salts,  were  all  that 
were  required  to  give  good  bright-colored  oils  of  good  drying  qualities 
with  firm  films,  and  not  all  of  these  amounts  of  driers  were  taken  up 
by  the  oil,,  but  some  were  recovered  in  the  residuum. 

The  sulphate  of  zinc  boiled  with  linseed-oil  simply  removes  the 
vegetable  and  mucilaginous  substances  that  impair  its  drying  power; 
it  does  not  impart  any  catalytic  power  to  the  oil  to  draw  oxygen 
from  the  air. 

Peroxide  of  manganese,  umber,  red  lead,  and  litharge,  all  dissolve 
in  the  oil  and  impart  oxygen  to  it,  and  act  catalytically  to  take  up 
more  oxygen  from  the  air  to  renew  what  they  have  lost,  and  in  so 
doing  further  oxidize  the  oil. 

Thome  and  Brin's  Oxygen  Process. 

In  this  process  for  oxidizing  oil,  pure,  or  nearly  pure,  oxygen 
gas  in  a  finely  divided  stream  is  poured  through  the  oil  at  natural 
temperatures,  or  moderately  heated,  if  desired.  The  process  occupies 
from  2  to  7  hours,  but  a  small  quantity  of  the  usual  driers  shortens 
the  time  of  oxidation.  The  color  and  drying  qualities  of  the  oil 
oxidized  by  this  process  are  excellent.  The  consumption  of  oxygen 
gas  varies  from  2000  to  4000  cubic  feet  per  ton  (250  gallons)  of  oil, 
according  to  the  degree  of  oxidation  required. 

The  principal  difficulty  in  this  process  is  in  generating  the  supply 
of  oxygen  gas,  which  requires  a  more  complicated  plant,  chain  of 
operations,  and  intelligence  on  the  part  of  the  workmen  than  that 
connected  with  the  quicker  processes  of  the  bung-hole  boil,  where  a 
bung-starter,  a  scoop,  and  a  dish  of  metallic  salts  are  all  that  are 
necessary  for  a  manufacturing  outfit. 

In  the  manufacture  of  corticine  (resembling  linoleum)  the  oil  is 
oxidized  at  a  high  heat,  350°  to  500°  F.,  until  it  begins  to  thicken 
and  get  ropy.  The  result  is  not  only  a  loss  by  evaporization,  but 


234  BOILING  LINSEED-OIL. 

the  oil  acquires  a  peculiar  sickish  smell  that  no  subsequent  treatment 
or  step  in  the  manufacture  is  able  to  remove. 

The  present-day  process  of  boiling  oil  upon  a  large  scale  as  prac- 
tised by  most  of  the  crushers  of  linseed  is  to  dissolve  4  pounds  of 
lead  oxide  or  litharge,  or  both,  in  5  gallons  of  well-aged  and  settled 
linseed-oil  at  a  temperature  of  about  250°  F.  for  a  short  time  or  until 
all  of  the  oxides  are  absorbed. 

This  mixture  if  allowed  to  cool  will  harden  into  a  firm  cake  of 
gum  (linolate  of  lead).  This  product  while  still  hot  is  mixed  with 
40  to  50  gallons  of  linseed-oil  heated  to  the  same  degree  to  coagulate 
the  albumin,  and  the  mixture  allowed  to  settle.  Five  hundred  or 
more  gallons  of  this  mixture  are  made  up,  and  while  hot  are  mixed 
with  a  large  tank  (5000  gallons  or  so)  of  raw  linseed-oil  also  heated 
to  about  200°  and  thoroughly  stirred  together.  This  is  commercial 
boiled  oil,  which  varies  in  character  according  to  the  quality  of  the 
linseed-oil  used  in  any  stage  of  the  process,  also  in  the  proportion  of 
the  oxide  oil  to  that  in  the  large  tank,  4,  6,  8,  or  10  to  1,  etc.  Lead 
oxide  and  a  small  quantity  of  manganese  oxide  make  a  better  drying 
oil  than  the  red  lead  alone. 

Varnish-makers  make  this  liquid  drier  for  use  by  local  painters r 
who  remove  4  or  5  gallons  of  raw  oil  from  the  barrel  and  replace 
them  with  the  same  quantity  of  the  liquid  drier,  and  then  roll  the 
barrel  around  or  stir  up  the  mixture  with  a  paddle-stick  for  their 
"bung-hole"  boiled  oil. 

Some  large  users  of  paint  oil  think  that  this  make  of  "bung-hole  " 
boiled  oil  is  as  good  as  that  supplied  by  the  large  manufacturers; 
but  this  is  doubtful,  as  all  of  the  albuminous  substances  in  the  bung- 
hole  oil  are  retained  unchanged,  and  they  are  subject  to  a  future 
decomposition  that  the  200°  of  heat  in  the  cooking  of  the  large  tank 
of  oil  coagulates,  and  they  settle  out  on  standing. 

Lead-  and  manganese-oxide  driers  made  from  resin,  or  resin-oil,, 
are  marketed  on  a  large  scale  at  18  to  20  cents  per  gallon,  while  a 
properly  made  linseed-oil  drier  cannot  be  furnished  for  less  than  3 
to  4  times  that  price. 

Double-boiled  oil  means  that  a  double  dose  of  drier  and  resin-oil  has 
been  put  through  the  bung-hole  process.  The  more  drier  the  poorer 
will  be  the  oil  product. 

No  two  manufacturers  of  boiled  oil  furnish  an  oil  of  the  same 
character  or  quality,  owing  to  their  different  manner  of  cooking  it 
and  the  amount  and  kind  of  drier  used,  etc.  The  name  "boiled  oil" 


BOILING  LINSEED-OIL.  235 

represents  about  as  uncertain  a  product  as  a  mixed  paint,  and  is 
simply  a  trade-name  for  an  extremely  varied  composition. 

The  reputation  of  the  dealer  or  manufacturer  is  the  best  guide. 
Adulterations  by  the  use  of  resin-oils  are  to  be  especially  looked  for  in 
all  commercial  grades  of  boiled  oil. 

Boiled  oil  is  a  misnomer.  Linseed-oil  never  boils;  if  it  did  it 
would  decompose  into  a  permanent  gas.  The  degree  of  heat  applied 
in  the  process  of  so-called  boiling  by  careful  manufacturers  is  only 
that  necessary  to  evaporate  some  of  the  water  natural  to  the  oil. 
This  degree  and  amount  of  heat  also  coagulates  the  mucilage  and 
albuminous  substances,  so  that  they  are  released  from  the  acid  oils, 
and,  by  their  greater  weight,  are  deposited  as  soon  as  the  oil  comes  to 
a  state  of  rest  after  the  heating  process.  In  oil  from  ripe  linseed,  if 
given  time  to  age  after  crushing,  the  mucosities  and  some  of  the  water 
in  its  composition  (about  5  per  cent),  that  is  loosely  held  in  com- 
bination, will  settle  and  can  be  filtered  out  or  drawn  off,  leaving  the 
oil  bright  and  clear,  and  with  a  minimum  amount  of  water  to  be 
evaporated  in  the  process  of  drying  as  a  raw  oil.  Storage  in  tanks 
for  3  or  more  months  still  further  improves  the  oil,  especially  if  the 
tankage  is  kept  at  a  moderately  warm  temperature.  This  fact  is 
taken  cognizance  of  by  the  varnish  manufacturers,  who  require  the 
best  quality  of  linseed-oil  for  their  products,  and  from  the  better 
prices  they  receive  for  their  wares,  can  secure  the  best  qualities  of 
•oil  in  the  market  at  a  price  that  the  manufacturers  of  cheap  paints 
-cannot  compete  with.  Storage  of  three  or  more  millions  of  gallons 
is  carried  by  some  of  the  best  varnish  and  linseed-oil  trade  dealers. 
'The  natural  result  of  such  selection  and  storage  is,  that  the  oil  is  well 
aged,  clear,  and  bright,  and  can  be  depended  upon  as  a  vehicle,  unless 
afterward  adulterated  or  abused  in  its  application. 

As  stated  before,  all  driers  are  injurious  to  linseed-oil,  and  the 
marked  inferiority  of  trade  boiled  oil  to  raw  linseed-oil  is  due  to  the 
driers  used,  whether  liquid  or  solid,  and  not  wholly  to  the  removal  of 
the  water  and  mucosities  in  the  boiling  process.  The  salts  and  oxides 
of  metals  that  constitute  the  solid  class  of  driers,  that  enable  the  oil 
to  dry  promptly,  are  generally  added  in  great  excess  of  the  amount 
actually  necessary  for  aiding  the  natural  tendency  of  the  oil  to  dry. 
That  portion  of  the  driers  in  excess  remains  in  the  dried  coating, 
and  acts  as  a  carrier  of  oxygen,  to  attack  the  pigment;  and  the  subse- 
quent failure  of  the  coating  is  assured. 


CHAPTER  XXIV. 

DRYING   OF   LINSEED-OIL. 

MULDER'S  experiments  in  the  drying  of  siccative  oils  deter- 
mined that  there  were  two  periods  in  the  drying  of  a  paint,  oil,  or 
varnish  coating.  The  first  period  occurs  in  the  early  months,  and 
is  wholly  due  to  the  changes  in  the  drying  elements  of  the  oil,  and 
while  these  changes  are  in  progress,  the  covering  is  always  dry  to 
the  touch  and  remains  elastic.  This  period  is  of  longer  duration  if  the 
coating  is  not  exposed  to  the  direct  rays  of  the  sun.  During  the 
period,  100  parts  of  the  oil  at  ordinary  temperatures  increase  in 
weight  to  111  or  112  parts,  but  when  warmed  to  170°  F.  it  loses  4  to  5 
parts.  In  the  direct  sunlight  for  all  the  period  of  drying,  the  oil 
gains  about  7  parts. 

During  the  second  period  the  oil  becomes  hard  and  firm  as  a  resin- 
ous coating,  the  change  being  in  the  non-drying  elements  of  the 
oil.  The  increase  in  weight  of  the  oil  is  not  so  great,  because  the 
breaking-up  of  the  glycerine  element  has  taken  place  in  the  first 
period.  These  total  changes  amount  to  about  a  quart  of  oil  in  1000 
square  feet  of  painted  surface. 

The  influence  of  heat  in  drying  a  paint  or  varnish  is  apparent 
when  it  is  considered  that  in  the  ordinary  drying  of  either  to  a  firm, 
hard  coating,  21  per  cent  of  oxygen  has  been  absorbed  from  the 
atmosphere  or  driers,  yet  a  further  exposure  to  the  heat  of  the  sun 
until  the  coating  becomes  hard  and  resinous  ensures  a  loss  of  3  to  5 
per  cent  of  this  amount.  It  is  to  be  recommended  that  this  drying 
and  loss  be  had  while  the  coatings  are  still  elastic,  because  this  loss  in 
substance  (due  to  the  changes  in  the  non-drying  oil)  takes  place 
while  the  vehicle  is  soft  and  elastic  enough  to  adjust  itself  to  the  loss 
in  volume. 

Oil  or  varnish  dried  in  the  direct  hot  rays  of  the  sun  are  not  as 
durable  as  when  dried  in  the  shade,  the  effect  of  the  sun  being  to 
evaporate  the  volatile  elements  of  the  glycerine  ethers  instead  of 
absorbing  them  into  the  non-drying  or  fatty  acids  of  the  oil.  A 

236 


DRYING  OF  LINSEED-OIL. 


237 


frost  on  a  drying  oil  or  paint  is  fatal  to  its  integrity ;  the  coating  will 
peel  in  strips  and  cannot  be  restored;  but  paint  dried  in  clear  cold 
weather  (not  frosty  weather,  that  leaves  a  sweat  in  and  on  the  coat- 
ing, as  the  temperature  rises)  lasts  longer  than  a  sun-dried  coating. 

It  is  probable  that  the  cold-dried  coating  lasts  longer  for  the  reason 
that  its  change  into  the  hard-soap  compound  has  been  delayed,  and 
being  more  elastic  than  the  sun-dried,  the  bond  between  the  pigment, 
oil,  and  surface  covered  is  more  effectually  made.  Hence  some  lead  in 
the  from  of  a  drier  is,  therefore,  an  advantage  in  an  oil  compound  or 
paint,  if  the  pigment  does  not  contain  it.  The  manganese  driers  are 
especially  unreliable  if  applied  in  cold  or  unfavorable  weather. 

The  percentage  gain  in  weight  of  a  cold-drawn  raw  linseed-oil, 
exposed  for  drying  under  different  conditions,  was  as  follows : 


Days 
Exposed. 

In  Darkness. 

Under 
Unclouded 
Glass. 

Under 
Blue  Glass. 

Under 
Yellow  Glass. 

Under 
Red  Glass. 

Under 
Green  Glass. 

10 

.000 

0.126 

0.089 

0.012 

0.009 

0.005 

20 

.001 

0.236 

0.245 

0.041 

0.027 

0.023 

40 

.003 

0.258 

0.376 

0.181 

0.082 

0.139 

60 

.007 

0.298 

0.388 

0.319 

0.178 

0.269 

90 

.013 

0.272 

0.357 

0.417 

0.338 

0.401 

120 

.018 

0.273 

0.360 

0.442 

0.376 

0.438 

150 

.035 

0.300 

0.399 

0.474 

0.441 

0.485 

After  150  days  the  gain  in  weight  was  the  greatest  in  the  follow- 
ing order:  green,  yellow,  red,  blue,  and  uncolored.  The  application 
of  a  dry  heat  at  temperatures  of  150°  to  170°  F.  dries  a  raw  oil  from 
30  to  50  times  faster  than  an  open-air  exposure  under  the  general 
conditions  of  summer  weather.  Light,  heat,  and  air  are  all  necessary 
elements  to  properly  dry  an  oil-paint  or  varnish  coating  of  any  qual- 
ity. The  slow-drying  oils  gain  more  weight  than  the  quick-drying. 

Raw  linseed-oil  has  a  specific  gravity  of  0.9299  to  0.931,  and  the 
same  oil  boiled,  that  of  9.411.  One  hundred  parts  of  drying  and 
non-drying  elements  in  the  raw  oil  in  the  process  of  kettle-boiling 
lose  8  parts  of  glyceride  ether  and  one  part  of  the  carbon  and  hydrogen 
from  the  non-drying  oil  or  fatty  acids.  This  is  equal  to  9  parts  in  all, 
leaving  90  parts  that  absorb  21  parts  of  oxygen  from  the  atmosphere 
when  the  oil  is  fully  dried,  the  100  parts  of  the  raw  oil  becoming  111 
when  dry. 

The  presence  of  the  glycerine  ether  and  the  changes  it  effects 
between  the  oleic,  stearic,  margaric,  palmitic,  and  other  acids  forming 
the  non-drying  oil  and  the  drying  elements  to  form  the  linoleic  com- 


238  DRYING  OF  LINSEED-OIL. 

pound,  appears  to  be  necessary,  as  Mulder  indicates,  who  added  oxide 
of  lead  to  the  oil  that  formed  with  the  glycerine  a  hard-lead  soap. 
The  drying-oil  acids  were  then  washed  away  by  ether,  the  ether  was 
drawn  off,  and  the  strictly  siccative  part  of  the  oil  set  free.  When 
this  oil  was  spread  and  exposed  for  drying,  it  gained  in  weight  8  per 
cent  in  3  days,  14  per  cent  in  7  days,  17J  per  cent  in  30  days,  but  did 
not  become  fully  dry  in  many  months. 

A  putty  made  from  thick  glycerine  and  dry  white  lead  or  litharge, 
or  both,  will  harden  in  from  15  to  45  minutes. 

The  conclusions  of  Mulder  and  many  other  experimenters  in  this 
line,  as  well  as  those  of  practical  painters,  are :  That  any  metallic  salt 
used  as  a  free  or  bung-hole  drier,  or  as  a  heat-combined  drier,  that  is 
so  energetic  in  action  as  to  destroy  the  glyceride  element  instead  of 
aiding  it  to  effect  its  change  into  a  drying  oil,  is  an  injury.  The  oil 
can  be  made  to  dry  by  evaporation  by  adding  volatile  driers,  but  it 
does  not  form  a  firm  reliable  coating,  like  that  produced  by  a  natural 
resinification. 

The  London  Journal  notes  that  Lippert,  experimenting  with  oils 
and  varnishes  in  order  to  observe  the  effect  of  the  absorption  of 
oxygen  during  the  process  of  drying,  finds  that  for  boiled  linseed-oil 
the  less  drier  used  the  better,  whether  the  drier  be  a  manganese 
resinate  or  lead  oxide.  After  its  application  upon  a  surface,  a  coat- 
ing of  this  kind  increases  in  weight  while  drying.  The  higher  the 
proportion  of  drier,  the  sooner  is  the  maximum  of  absorption  reached, 
and  the  sooner,  also,  the  coating  begins  to  lose  weight  again.  Con- 
versely, the  smaller  the  proportion  of  the  drier,  the  larger  is  the  total 
weight  of  oxygen  taken  up.  After  4  weeks,  the  varnish  containing 
2  per  cent  of  manganese  had  commenced  to  soften  again,  and  stuck 
to  the  palm  of  the  hand.  The  preparation  containing  only  0.15  per 
cent  of  manganese  was  distinctly  the  best.  With  litharge,  also,  the 
larger  the  proportion  of  drier  the  sooner  the  varnish  attained  its 
maximum  weight,  and  the  less  total  oxygen  was  absorbed.  All  the 
films  were  equally  hard  to  the  touch  when  they  had  reached  their 
maximum  weight;  but  after  4  weeks  they  softened  again — this  being 
more  especially  noticeable  with  the  specimens  containing  much  of 
the  drier.  Additions  of  litharge  above  2J  per  cent  made  no  appre- 
ciable difference  in  the  absorbing  power;  while  for  practical  work 
the  proportion  of  the  lead  ought  evidently  to  be  kept  lower  than  that 
permissible  with  the  manganese  salts  (see  Thorp's  Experiments, 
Boiling  Oil,  Chapter  XXIII.).  The  reason  why  such  coatings  soften 


DRYING  OF  LINSEED-OIL.  239 

again  after  becoming  dry  is  not  yet  known.  It  may  be  found  to  depend 
on  the  presence  of  an  excess  of  drier,  or  of  an  unsuitable  one.  It  does 
not  prove  adulteration  with  rosin  or  rosin  oil.  It  may  be  due  to 
oxidation  of  lead  linoleate  into  a  liquid  turpentine-like  body  by  pro- 
longed exposure  to  the  air.  Science  indicates  no  better  way  of  testing 
a  drying  varnish  than  by  the  finger. 

Prof.  Max  Pettenkofer  removed  the  non-drying  acids  from  freshly 
dried  linseed-oil  skins  by  ether,  leaving  an  elastic  caoutchouc-like 
substance,  which  by  degrees  hardened  and  became  brittle.  On 
further  exposure  to  the  air  it  separated  easily  into  thin  flakes;  in 
fact,  it  hardened  and  cracked  like  the  fossil  resins  or  the  coniferse 
crude  gums. 

These  deductions  from  a  long  chain  of  closely  and  carefully  con- 
ducted experiments,  not  only  in  the  laboratory,  but  in  the  application 
of  oil,  paint,  and  varnish  coatings,  with  all  classes  of  pigments,  spread 
over  ferric,  wood,  and  mineral  surfaces,  appear  to  be  ignored  in  many, 
if  not  in  most,  of  the  present-day  compositions  of  paints  and  oils. 

The  larger  amount  of  mucilage  in  all  unripe  or  damaged  linseed 
and  other  vegetable  oils,  when  freshly  made,  or  that  have  been  ex- 
tracted by  the  bisulphide  of  carbon,  the  hot  or  steamed  seed  pro- 
cesses, deteriorates  the  quality  of  the  oil,  and  such  oil  even  if  it  is  to  be 
kettle-boiled,  is  benefited  by  long  standing  to  allow  some  of  the  "mu- 
cosities"  or  " drops"  to  settle.  The  amount  of  these  preliminary 
"foots"  is  from  one  to  one  and  one-tenth  part  in  one  hundred  parts  of 
oil.  The  greener  or  poorer  the  class  of  seeds  from  which  the  oil  is  made 
the  greater  will  be  the  amount  of  "  foots." 


CHAPTER  XXV. 

LIN  SEED -OIL   TESTS   FOR  ADULTERATIONS. 

THERE  are  many  methods  of  testing  the  purity  of  linseed-oil. 
The  specific  gravity  test  is  of  small  moment,  even  if  not  altogether 
unreliable,  as  the  commercial  adulterant  oils  (over  one  hundred  in 
number)  vary  in  specific  gravity  only  seven-hundredths  of  a  degree 
Baume,  and  no  reliable  chemical  test  has  been  found  that  is  practical 
for  the  ordinary  analyst. 

One  difficulty  lies  in  procuring  a  chemically  pure  oil  to  make  the 
comparison  with  the  reactions  caused  by  sulphuric  and  nitric  acids, 
and  caustic-soda  treatment  for  the  color  changes  in  the  sample  tested. 
The  linseed  for  such  an  oil  must  be  picked  over  with  the  greatest  care, 
selected  from  fully  ripe  and  full-weight  seeds,  and  pressed  in  seed  bags 
that  have  never  been  used  before. 

The  result  of  an  application  to  a  large  number  of  the  most  responsi- 
ble oil-seed-pressing  firms,  was  that  not  one  could  furnish  a  sample 
with  less  than  5  per  cent  of  other  seed-oil  in  it,  and  most  of  the  best 
commercial  brands  contained  over  12  per  cent. 

Approximation  chemical  tests  are  numerous,  but  in  all  cases  a 
sample  of  known  quality  of  linseed-oil  should  be  used  for  comparison, 
even  if  it  is  not  a  chemically  pure  oil.  Abbe's  and  other  refractom- 
eters  are  used  to  test  the  purity  of  linseed-oil,  but  their  use  is  too 
complicated  for  any  one  but  an  experienced  chemist. 

All  the  fatty  oils  change  color  when  brought  into  contact  with 
strong  sulphuric  acid.  If  a  drop  be  added  to  8  or  10  drops  of  an  oil 
placed  on  a  glass  plate  resting  on  white  paper,  the  following  colors 
are  immediately  produced.  Olive-oil  turns  a  deep  yellow,  gradually 
becoming  green.  Sesame-oil,  a  bright  red.  Colza-oil,  a  greenish- 
blue  aureola.  Poppy-seed  oil,  a  pale  yellow  with  a  dingy  gray  look. 
Hempseed-oil,  a  distinct  emerald  green.  Linseed-oil  turns  brown- 
red,  changing  to  a  black  brown. 

Prof.  F.  C.  Calvert's  chemical  method  of  testing  oils  by  acids, 

240 


LINSEED-OIL   TESTS  FOR  ADULTERATIONS.  241 

for  the  color  changes,  is  given  in  full  in  Watts's  Diet,  of  Chem.,  Vol. 
IV,  p.  183. 

Mineral  oil  or  petroleum  in  any  form  cannot  be  added  to  linseed- 
oil  to  exceed  5  per  cent  without  affecting  its  drying;  and  10  per 
cent  prevents  its  drying  other  than  as  a  thin  skin  impervious  to  the 
air,  and  the  oil  remaining  green  beneath  is  liable  to  blister  or  peel  on 
exposure  to  sunlight.  It  does  not  bond  to  the  pigment  or  surface 
coated. 

If  a  tin  plate  coated  with  a  mixture  of  a  vegetable  and  a  mineral 
oil  be  viewed  at  different  angles  in  strong  sunlight,  the  mineral  oil 
can  be  detected  by  the  iridescent  or  metallic  play  of  color,  which 
petroleum  imparts  to  all  vegetable  oils.  So  characteristic  is  this, 
that  a  little  experience  will  enable  a  painter  to  readily  detect  mineral 
oil  when  present  even  in  a  small  quantity.  This  feature  is  in  some 
degree  disguised  or  palliated  by  treating  the  mineral  mixed  oil  with 
caustic  lime,  chalk,  etc.,  and  adding  an  excess  of  strong  free  driers, 
which  may  suppress  the  iridescent  hues;  but  if  the  sample  is  ignited, 
the  marked  pungent  odor  of  burning  petroleum  vapor  is  readily 
recognized. 

Cottonseed-oil,  a  semi-siccative  oil,  was  formerly  mixed  in  large 
quantities  with  linseed-oil.  Its  specific  gravity,  color,  taste,  and  odor 
are  almost  identical  with  linseed-oil.  It  requires  a  large  amount  of 
driers  either  compounded  with  it  by  heat  or  as  free  driers  to  enable 
it  to  dry.  Its  tendency  at  the  best  is  to  harden  and  crack  the. over- 
lying coatings;  also  to  crack  in  cold  weather,  from  its  non-elastic 
condition  due  to  the  driers  used.  Crude  cottonseed-oil  treated  with 
strong  ammonia  mixed  with  3  parts  of  water,  gives  an  opaque  brown 
color.  Refined  cottonseed-oil,  similarly  treated,  gives  a  brownish  or 
dull  opaque  yellow.  Pure  linseed-oil  similarly  treated  for  comparison, 
gives  a  bright,  but  semi-transparent  yellow.  Mixtures  of  both  oils 
give  an  intermediatory  color,  that  a  little  experience  will  enable  a 
painter  to  determine  approximately  the  amount  of  the  mixture. 

A  quick  test  by  cold  is  to  place  a  sample  of  the  cottonseed-oil, 
mixture  on  a  piece  of  glass  alongside  of  a  known  sample  of  linseed-oil, 
and  place  the  glass  in  a  refrigerator  or  on  a  piece  of  ice.  In  a  short 
time  the  impure  sample  will  become  discernibly  thicker  than  the 
linseed-oil. 

Crude  cottonseed-oil  produces  a  brown  deposit  on  a  piece  of 
bright  copper  foil  (to  be  had  from  all  dealers  in  chemicals)  if  left  in 
contact  with  it  in  a  warm  place  for  3  or  4  days.  The  price  of  cotton- 


242  LINSEED-OIL  TESTS  FOR  ADULTERATIONS. 

seed-oil  of  late  years  has  become  so  nearly  that  of  linseed-oil  that  its 
use  to  adulterate  the  latter  has  sensibly  diminished.  There  is,  how- 
ever, a  combination  of  the  damaged  seed  oils  from  both  crops,  for 
which  there  is  always  a  demand  to  furnish  a  mogrel  linseed-oil  at  a 
cut-rate  price. 

Resin  oils  are  freely  used  to  adulterate  linseed-oil,  even  by  firms 
whose  business  reputations  should  warrant  more  honest  wares.  Resin 
mixes  readily  with  linseed-oil,  and  whether  its  grade  be  light  or  heavy, 
it  cannot  be  detected  by  its  specific  gravity.  For  a  quick  test  of  its 
presence,  shake  up  a  spoonful  of  the  sample  with  5  times  the  quantity 
of  strong  alcohol;  pour  off  the  alcohol  and  add  to  it  a  clear  solution 
of  sugar  of  lead;  a  cloudy  precipitate  shows  the  presence  of  resin. 

Resin-oil  can  also  be  detected  by  the  remarkably  nauseous  after- 
taste produced  by  it  when  touched  by  the  tongue.  The  odor  of  the 
oil  is  not  recognizable  in  the  sample  unless  ignited,  when  it  becomes 
decidedly  different  in  odor  from  ignited  linseed-oil.  If  the  cork  of 
the  sample  bottle  squeaks  when  it  is  twisted  around  in  the  neck  of  the 
bottle,  no  further  test  is  necessary  to  denote  its  presence. 

Linseed-oil  adulterated  with  resin-oil  of  any  grade  is  readily  de- 
tected by  passing  a  current  of  chlorine  gas  through  the  sample  oil, 
which  is  rapidly  blackened  if  any  appreciable  amount  of  resin  is  present. 

Resin-oil  is  especially  to  be  looked  for  in  boiled  oil.  It  never 
hardens  completely,  and  makes  the  coating  "  tacky."  If  any  consid- 
erable amount  of  resin  is  present  in  a  linseed-oil  that  has  received  an 
excess  of  driers  to  harden  the  coating,  the  coating  will  be  brittle  and 
crumble  easily  on  a  short  exposure  to  the  atmosphere,  particularly 
in  summer  weather,  or  by  exposure  to  heat. 

Menhaden  and  porgy  fish-oils  are  used  freely  to  adulterate  linseed- 
oil,  especially  in  many  of  the  mixed  paints  and  pastes.  The  price 
of  these  oils  is  only  about  one-half  that  of  a  poor  linseed-oil.  Fish- 
oil  in  the  twentieth  century,  used  as  an  adulterant  of  linseed-oil,  com- 
prises almost  anything  from  a  whale  to  a  mossbunker,  with  the  oil 
from  dead  animals  frequently  added  to  help  out  the  abomination. 
The  fish-oils  dry  slowly,  but  surely,  if  fortified  by  strong,  free  driers. 
Fish-oils  used  for  a  tin-roofing  paint  will  stick  longer  than  a  linseed-oil 
paint,  as  they  do  not  dry  so  hard.  They  are  more  affected  by  cold 
than  linseed-oil,  and  whatever  paint  coating  is  spread  over  one  with  a 
fish-oil  vehicle  will  probably  peel  in  a  short  time. 

Crude  menhaden-oil  when  cold  has  but  little  odor,  and  in  color 
closely  resembles  linseed-oil.  By  strongly  heating  a  sample  the  fishy 


LINSEED-OIL  TESTS  FOR  ADULTERATIONS.  243 

odor  is  developed.  Skilfully  mixed,  the  odor  is  hard  to  detect,  even 
when  moderately  heated. 

Place  a  sample  of  a  known  quality  of  linseed-oil  and  one  of  the 
oils  to  be  tested,  in  separate  test-tubes,  coik,  and  then  heat  together 
in  a  hot  water-bath;  if  the  suspected  oil  gives  off  an  odor  of  acroldn 
(oxidized  glyceride)  similar  to  that  of  the  smoldering  wick  of  a  tallow 
candle,  fish-oil  of  some  grade  and  amount  is  present. 

One  of  the  most  reliable  tests  of  the  purity  of  linseed-oil,  and  one 
that  does  not  have  to  be  felt  for  as  in  the  preceding  tests,  and  is  equally 
available,  is,  viz. :  Add  to  100  parts  of  the  oil  by  weight,  one-half  of  one 
per  cent  by  weight  each,  of  litharge  and  red  lead  well  stirred  together. 
Heat  in  any  convenient  vessel,  and  in  any  manner,  until  an  immersed 
thermometer  reaches  480°  to  500°  F.  A  feather  from  a  feather  duster 
or  chicken's  wing  will  answer  instead  of  a  thermometer.  If  the 
feather  when  dipped  in  the  hot  oil  curls  up  with  a  crackling  sound, 
it  indicates  an  approximate  temperature.  A  small  current  of  air 
from  a  bellows  or  other  source  should  be  blown  through  the  oil  as  it 
is  being  gradually  heated.  A  small  glass  tube  and  a  piece  of  drug- 
gist's rubber  tubing  are  readily  available  for  this  part  of  the  appa- 
ratus. Small  samples  are  taken  out  from  time  to  time  and  cooked 
on  an  iron  plate.  As  soon  as  the  samples  appear  stringy  when  cold, 
allow  the  oil  to  cool,  stirring  it  constantly  during  the  cooling.  If  the 
oil  is  solid  and  firm  when  cold  the  sample  is  of  good  quality.  A  poor 
oil  will  be  sticky  and  more  or  less  fluid,  and  of  bad  odor. 

Animal  oils  can  be  detected  by  their  odor  when  the  sample  is 
heated,  also  by  the  addition  of  nitric  or  sulphuric  acid,  either  of  which 
gives  an  intense-red  color  to  fish-oils.  The  adulteration  of  mineral 
oils  is  readily  discovered  by  the  process  of  saponification,  when  these 
substances  rise  to  the  surface.  The  saponification  number,  or  the 
number  of  milligrams  of  K.HO  required  to  saponify  linseed-oil,  is 
190.2  to  192.7.  This  number  for  many  adulterated  oils  is  as  low  as 
180.  The  iodine  number  of  linseed-oil  is  158.7  to  159.78;  that  of 
fatty  acids,  159.85. 

It  is  frequently  necessary  to  clarify  linseed-oil.  The  following  are 
a  few  of  the  methods : 

Heat  the  oil  slowly  up  to  300°  C.  (570°  F.)  either  by  itself  or  with 
the  addition  of  from  1  to  5  parts  of  either  caustic  lime,  carbonate  of 
lime,  calcined  magnesia,  or  carbonate  of  magnesia,  and  keep  the  oil 
at  the  above  temperature  for  2  hours,  and  then  allow  it  to  cool  uncov- 
ered and  undisturbed.  Transfer  it  to  a  settling-tank  to  deposit  and 


244  CLARIFYING  LINSEED-OIL. 

clarify.  When  clear  transfer  it  to  another  vessel.  Clarified  oil  should 
not  be  kept  in  contact  with  the  deposit  or  "  drops." 

Mulder  recommends  the*  clearing  of  turbid  linseed-oil  by  washing 
it  with  its  own  volume  of  warm  water  containing  some  common  salt. 

Sulphuric  acid  is  used  for  clarifying  linseed-oil,  particularly  adul- 
terations of  it.  Its  action  is  to  carbonize  the  fibrine  elements  of  the 
fish-oils  and  the  mucilaginous  substances  in  the  vegetable  oils,  and 
to  deposit  them  in  the  so-called  " foots"  or  " drops."  Its  action  is 
injurious  to  linseed-oil  in  general,  for  it  removes  by  carbonization 
a  part  of  the  fatty  acids,  or  non-drying  elements,  and  all  of  the 
glyceride  ethers,  the  latter  being  essential  to  the  changes  necessary 
to  form  a  firm,  hard  coat  from  the  oil  when  dry.  Acid-treated  oils  are 
liable  to  dry  on  the  exterior  only,  and  never  become  hard  or  firm. 
Acid-treated  oils  require  long,  careful,  and  repeated  washings  with 
warm  water  in  the  form  of  an  air-blown  spray  through  the  body  of  the 
oil  in  a  deep  tank  to  eliminate  the  acid,  which  is  seldom  thoroughly 
done.  The  acid,  besides  delaying  the  drying,  will  attack  the  metallic- 
base  pigments  afterward  associated  with  it  in  the  paint. 

Graphite  and  carbon  pigments  are  less  affected  by  sulphuric  acid 
in  the  oil  than  any  other  class  of  pigments. 

Graphite  paint-skins  detached  from  the  metallic  plates  on  which 
they  had  been  spread  and  dried,  when  immersed  in  5  per  cent  solu- 
tions of  sulphuric  acid,  lost  in  weight  from  1.5  to  1.7  per  cent,  but 
were  not  affected  in  lustre,  strength,  or  elasticity. 

This  result  indicates  their  superior  qualities  for  heavy  coatings 
for  roofing  paint,  and  in  other  locations  where  any  sulphur  element 
can  reach  them,  whether  from  the  vehicle  or  the  atmosphere. 

The  results  of  Mulder's  experiments  with  sulphuric-acid-treated 
oils  to  ascertain  their  qualities  were  that  they  did  not  begin  to  dry 
materially  under  8  days.  At  the  end  of  3  months  the  samples  had 
gained  15  per  cent  in  weight,  but  lost  3  per  cent  of  this  when  heated 
to  150°  F.  for  a  short  time.  Also  a  strong  heat  from  the  sun  for  a 
number  of  summer  days  produced  the  same  effect. 

Pure  linseed-oil,  not  treated,  gained  10  per  cent  in  the  same 
period  and  lost  2.5  to  3  per  cent  on  heating  it.  The  acid  did  not 
affect  the  drying  elements  in  the  oil,  only  the  non-drying  ones,  as 
noted  before. 

The  colors  of  the  acid-treated  oils  were  not  materially  affected  by 
the  process;  generally,  they  were  brighter  for  the  treatment. 

Sulphuric-acid-treated  oils  being  naturally  of  a  fatty  or  non-dry- 


LINSEED-OIL  SULPHURIC-ACID  OILS.  245 

ing  character,  if  ground  in  a  hot  mill  will  develop  this  feature  more 
fully. 

Sulphuric  acid  in  the  oil  or  pigment  appears  to  take  kindly  to 
wooden  surfaces  as  a  priming  coat;  at  least  the  disintegrating  effect 
of  the  acid  is  not  so  marked  as  upon  metal.  All  sulphuric-acid-treated 
oils  have  a  tendency  to  increase  the  galvanic  action  in  all  paints  made 
from  them,  that  are  spread  on  wooden  surfaces.  When  used  on 
metallic  bodies  electrolysis  is  increased. 

The  following  table  *  gives  the  weight  in  grains  of  sulphur  in  a 
gallon,  of  a  number  of  the  oils  when  burned  by  means  of  a  wick  floating 
in  the  oil,  and  condensing  in  a  sulphur  apparatus  the  vapors  of  com- 
bustion, the  same  way  as  sulphur  is  determined  in  coal-gas : 

Name  of  Oil.  ^Ter^ffi:^ 

Linseed-oil  (La  Plata) trace. 

Cottonseed-oil. trace. 

Olive-oil none. 

Groundnut-oil none. 

Sperm-oil,  ordinary 2.3 

"        "    bottle-nose 3.1 

Cocoanut-oil 3.7 

Neatsf  oot-oil 4.7 

Cod-oil 5.8 

Rape-oil  (Jamba) 11.3 

"      "  pure  brown 14 . 2 

"      "   ordinary  brown 17.4 

"      "  brown,  refined  with  sulphuric  acid 16.8 

"      "         "            "          "     fullers'  earth 10 .0 

"      "         "      (Ravision's) 19. 1 

Russian  mineral  oil,  crude,  0 . 908 20 . 5 

"             "        "    burning 10 .3 

American  mineral  oil,  water-white 8.1 

"              "        "    burning 16.3 

"    safety 14.0 

Scotch  mineral  oil,  used  for  making  gas 49 .8 

Water  in  Linseed-oil. 

Pure  raw  linseed-oil  contains  over  5  per  cent  of  combined  water, 
and  the  commercial  or  poorer  grades  of  the  oil  frequently  contain  10 
per  cent.  Twenty  per  cent  of  water  can  be  stirred  into  linseed-oil  by 
a  painter's  paddle,  and  over  10  per  cent  more,  if  the  mixture  is  run 
through  ;&  mixing-mill,  either  with  or  without  a  pigment. 

*  Chemical  News,  also  Scientific  American  Supplement,  July  20, 1895.  Experi- 
ments by  Wm.  Fox  and  D.  G.  Riddick. 


246  WATER  IN  LINSEED-OIL. 

Mixed  white-lead  paint  (pure  or  adulterated)  will  form  an  emul- 
sion with  its  own  bulk  of  water  if  run  through  the  mill,  and  the  water 
does  not  separate  to  any  great  degree,  unless  it  stands  for  many  weeks, 
and  then  being  at  the  bottom  of  the  can  or  package,  escapes  notice. 

The  covering  or  spreading  power  as  well  as  the  coloring  power  of 
such  mixtures  are  of  the  poorest  character;  at  least  an  extra  coat  and 
often  two  are  necessary  to  present  any  sort  of  a  creditable  appearance. 
They  dry  solely  by  evaporation  through  the  outer  skin  of  the  paint, 
leaving  it  porous,  and  where  moisture  can  escape,  the  same  element 
containing  other  atmospheric  gases  can  enter  and  they  are  more  de- 
structive than  the  moisture  they  replace.  All  water-oil  mixtures  dry 
flat  and  lifeless.  The  use  of  alkalies  and  strong  metallic-salt  driers 
to  form  a  better  emulsion  does  not  materially  change  their  forced 
mechanical  association,  and  if  they  cannot  evaporate  and  escape  out- 
wardly, they  go  inward  and  condense  on  the  covered  surface,  form 
blisters,  and  peeling  results. 

It  is  almost  impossible  to  spread  a  water-oil  paint  in  the  cold 
without  heating  it.  If  spread  and  not  dry,  a  cold  night,  not  even 
approximating  a  frost,  will  ensure  a  blistering  and  peeling  the  next 
day.  Brushing  the  coating  over  with  turpentine  or  benzine  will  not 
prevent  or  correct  this  action,  which  will  take  place  regardless  of  the 
nature  of  the  pigment.  A  good  linseed-oil  paint  spread  on  a  cold  day 
(not  freezing  weather)  will  "take"  and  dry  if  a  little  extra  effort  on 
the  painter's  part  is  made  to  brush  it  out  well  and  by  using  a  little  more 
turpentine  for  the  drier  than  that  used  in  warmer  weather.  But  all 
painting  for  external  exposures  should  be  suspended  in  cold  weather, 
especially  on  all  ferric  structures,  unless  under  cover  and  in  a  warm 
room,  where  the  painted  surface  should  remain  until  the  paint  has  at 
least  "  set "  firmly,  or  until  it  has  dried  enough  to  bear  handling 
without  feeling  "tacky." 

Many  paint  chemists  deem  that  2  per  cent  of  water  added  to 
linseed-oil  in  excess  of  that  natural  to  it,  whether  made  from  ripe  or 
unripe  linseed,  is  not  detrimental  to  a  paint.  To  enable  the  oil  made 
from  unripe  seed  to  carry  the  extra  water,  it  is  rendered  slightly  alka- 
line, generally  by  adding  lime-water,  which  forms  with  the  oil  vehicle 
a  calcium  soap  that  thickens  the  paint,  so  that  it  never  settles  hard, 
and  is  easily  stirred  up,  consequently,  does  not  dry  hard. 

A  number  of  tests  for  free  water  in  linseed-oil  are:  Heating  the  oil 
to  212°  F.  for  a  short  time,  and  note  the  amount  lost  by  evaporation. 
Filtration  of  the  oil  after  heating  and  the  addition  of  dehydrated  copper 


WATER  IN  LINSEED-OIL.  247 

sulphate,  which  turns  bright  blue  when  added  to  the  oil.  A  strip  of 
gelatine  immersed  in  the  paint  for  10  or  more  hours  will  absorb  the 
free  water  and  swell  up.  Cool  the  paint  or  oil  for  a  few  hours  in  a 
refrigerator,  and  note  the  difference  in  its  spreading.  Heat  a  piece  of 
iron  to  a  bright  cherry-red  and  plunge  it  into  the  oil  or  paint.  If 
there  is  much  snapping,  it  indicates  the  presence  of  free  water  in  the 
mixture.  In  ordinarily  pure  oil  or  good  paint,  a  thick,  heavy  smoke 
without  explosion  or  snapping  will  follow  the  withdrawal  of  the  glow- 
ing test-iron. 


CHAPTER  XXVI. 

SUBSTITUTES   FOR   LINSEED-OIL. 

MANY  so-called  substitutes  for  linseed-oil  have  been  presented  to 
the  public  in  the  past,  and  at  present  they  are  numbered  by  the  hun- 
dreds in  the  Patent-office  records,  and  outside  in  the  formulae  of  the 
compounders  of  paints.  All  substitute  oils  are  as  uncertain  and  indefi- 
nite in  character  as  the  pigments  assembled  with  them. 

Generally,  a  low  grade  of  linseed-oil  is  the  base  for  the  vehicle,  to 
which  one  or  more  of  the  score  of  flax-dodders  or  buffums,  resin,  fish, 
mineral,  india-rubber,  and  soap-fat  oils  are  added.  These  are  mixed 
with  benzine  for  the  volatile,  also  with  manganese  or  other  strong 
metallic-salt  driers,  put  through  the  bung-hole.  No  heat  is  employed 
in  their  manufacture,  and  some  of  them  are  dangerous  to  sell,  or  spread 
even  when  cold. 

Purchasing  agents  and  master  painters  (except  in  a  few  cases) 
have  not  the  laboratory,  chemical  apparatus,  technical  knowledge, 
or  time  to  analyze  them  to  detect  the  fraud.  The  result  of  their  use 
comes  with  the  lapse  of  a  very  short  time,  when  the  scraper,  burning 
torch,  and  a  new  coating  are  the  only  remedies  for  the  evils  of  crazing, 
peeling,  or  decomposition  due  to  galvanic  action.  No  amount  of 
sophistry  can  change  the  fact  that  the  use  of  so-called  substitute 
oils  has  in  nearly  every  case  been  detrimental  to  the  paint  and  the 
covered  surface. 

Probably  80  per  cent  of  all  the  oils,  paints,  and  varnishes  manu- 
factured in  the  world  is  applied  to  structures  of  minor  importance, 
which  are  destroyed  by  causes  other  than  corrosion.  These  coatings 
are  quite  as  much  for  looks  as  for  physical  condition,  but  the  other 
20  per  cent  is  used  on  the  most  important  and  costly  engineering 
structures  of  our  time.  These  require  protection  from  corrosion 
from  the  hour  the  materials  leave  the  rolling-mill,  forge,  and  foundry, 
until  they  are  in  the  finished  structure,  and  need  more  then  than 
during  construction. 

248 


SUBSTITUTES  FOR  LINSEED-OIL.  249 

Among  the  recent  substitute  or  paint  oils  (dating  from  1895)  is 
the  substance  called  "Lucol,"  for  which  extraordinary  claims  are 
made,  viz.: 

"  Lucol"  *  is  a  paint  oil,  a  synthetical  compound,  made  by  a  secret 
process  from  materials  that  necessarily  are  a  part  of  the  manufac- 
turer's secret." 

What  it  is  as  a  chemical  compound,  or  as  a  manufactured  paint 
oil,  concerns  the  proprietors  of  it.  What  its  claims  are  for  superiority 
over  linseed-oil,  concerns  the  users.  As  set  forth  by  its  manufac- 
turers, its  characteristic  features  in  comparison  with  linseed-oil  are: 

"1.  Lucol  is  more  durable  than  linseed-oil,  which  dries  by  absorp- 
tion and  oxidation  and  only  to  a  small  degree  by  evaporation.  The 
reverse  is  the  case  with  lucol,  which  dries  principally  by  evaporation, 
hence  the  condition  of  the  atmosphere  to  which  it  is  exposed  while 
drying  must  be  considered. 

"2.  Lucol  sets  quicker  than  linseed-oil,  which  is  the  result  of 
evaporation  instead  of  the  oxidation  of  its  elements;  the  final  drying 
to  a  bone-hard  condition  requires  many  months.  The  retention  of 
its  elasticity  no  doubt  accounts  for  its  durability. 

"3.  Lucol  sets  sooner  and  dries  quicker  than  linseed-oil,  hence 
is  less  adhesive  for  dust,  and  does  not  wash  off  if  rained  on,  as  is  the 
case  with  other  vehicles. 

"4.  Lucol  gives  a  purer  white  with  white  lead  than  linseed-oil. 

"5.  Lucol  preserves  the  original  tint  of  the  pigment  longer.  More 
lucol  is  used  in  a  coating  than  when  linseed-oil  is  used.  The  gloss  is 
less  at  first  than  with  linseed-oil,  but  it  is  soon  ahead  in  this  respect. 
The  oil  is  the  life  of  the  paint. 

"6.  Lucol  can  be  flatted  with  a  much  smaller  proportion  of  tur- 
pentine than  with  linseed-oil." 

Other  advantages  are  set  forth,  but  all  are  more  adaptable  for  the 
use  of  lucol  on  surfaces  other  than  ferric,  and  have  been  answered 
elsewhere  in  this  work. 

The  Lucol  Company  says:  "We  extract  the  olein,  which  is 
carefully  refined  by  a  special  and  partly  secret  process,  and  by 
the  use  of  chemicals  it  is  converted  into  a  brilliant,  transparent, 
lemon-colored  oil.  It  contains  no  vegetable,  mineral,  or  fish  oil,  resin 
or  resin-oil,  varnish-gums,  benzine,  or  other  powerful  solvent  driers. 
Ignited  it  gives  off  an  odor  similar  to  that  of  burning  india-rubber, 

*  "  Lucol."  Excerpts  from  Painting  and  Decorating  Journal,  New  York, 
February,  1895. 


250  LUCOL  AS  A  PAINT  OIL.     OLEIN. 

entirely  different  from  the  odor  of  linseed-oil  in  combustion.  It  has 
an  unpleasant  odor  while  being  spread  and  in  drying,  wholly  unlike 
linseed-oil,  and  should  be  flowed  on  similar  to  a  varnish,  instead  of  being 
brushed  out  like  a  linseed-oil  coating. 

"Lucol,  in  the  form  of  a  paint,  resists  alkaline  substances,  sea- 
air,  sea-water,  and  covers  galvanized-iron  surfaces  without  peeling. 
Lucol  weighs  7  J  pounds  per  gallon,  and  is  placed  on  the  market  on  its 
me:its  as  a  synthetical  manufactured  oil,  wholly  unlike  any  other  sub- 
stitute compound  heretofore  offered  as  a  paint-oil." 

How  well  are  the  above  claims  founded?  "  We  extract  the  olein," 
etc.  This  at  once  destroys  the  claim  that  lucol  is  a  synthetical  com- 
pound. It  is  only  an  oil  made  with  a  vegetable,  an  animal,  or  a 
fatty  acid  base. 

All  of  the  solid  fats  and  oils  are  derived  from  two  sources.  The 
marine  animal  oils  are  obtained  from  the  cold-blooded  fish,  like  the 
cod,  menhaden,  etc.,  and  the  hot-blooded,  like  the  seal,  sperm,  and 
right  whale,  etc.  The  terrestrial  animal  oils  are  lard,  neat's-foot,  horse- 
bone,  tallow  (oleic  acid),  etc.  Both  classes  may  be  considered  as 
mixed  glycerides  of  oleic  acid  (C18H34O2),  stearic  acid  (C18H36O2),  and 
palmitic  or  benic  acid  (C16H  32^)2)  >  the  first  preponderating  in  the 
oils  and  the  two  last,  especially  the  stearic  (steaune),  in  the  fats. 

Oleic  acid  has  a  specific  gravity  of  0.808  at  65°  F.  and  is  the  liquid 
acid  obtained  by  the  saponification  of  non-drying  oils  and  liquid  fats, 
which  contain  a  different  glyceride  than  the  drying  oils.  The  propor- 
tion of  olein  differs  acco  ding  to  the  nature  of  the  fat  f  om  which  it 
is  obtained. 

Chevreul  prepared  it  by  boiling  human  fat,  lard,  goose-fat,  beef, 
and  mutton  suet,  filtering  the  solution  and  allowing  it  to  stand  for  24 
hours,  then  concentrating  it  a  little  by  evaporation,  adding  water  to 
separate  the  olein,  and  separating  the  liquid  from  the  solid  matter  by 
pressure.  Olein  thus  obtained  does  not  solidify  at  32°  F. 

Olein  is  also  prepared  from  olive-oil  and  other  glycerides  contain- 
ing it  by  pouring  upon  the  fat  a  cold  strong  solution  of  caustic  soda, 
which  saponifies  the  solid  fats  but  not  the  olein.  It  is  also  obtained 
from  olive  and  almond-oils  by  treating  them  with  cold  alcohol  and 
evaporating  the  solution. 

Pure  olein  is  a  colorless  oil  void  of  taste  and  smell,  insoluble  in 
water,  very  soluble  in  absolute  alcohol  or  ether.  Specific  gravity, 
0.90  to  0.92 ;  burns  with  a  bright  flame,  oxidizes  in  the  open  air,  yielding 
the  same  products  as  oleic  acid.  Crude,  or  carelessly  prepared,  the 


SUBSTITUTES  FOR  LINSEED-OIL.     OLEIN.  251 

olein  will  have  an  odor  distinctive  of  the  class  of  fats  from  which  it 
is  obtained. 

The  marine  oils  all  have  the  repulsive  fishy  odor  in  various  degrees, 
sperm-oil  being  the  hardest  to  locate.  The  terrestrial  animal  oils 
have  the  peculiar  sourish  odor  of  cooking  fats.  The  vegetable  oils 
have  a  sweetish  odor.  A  little  practice  with  a  heated  sample  will 
enable  the  most  of  them  to  be  recognized. 

Olein  is  also  extracted  from  the  organic  acids  in  soap-stock  or  the 
fats  left  in  the  by-products  in  the  refining  of  cottonseed-oil.  The 
fatty  acids  in  the  " foots"  are  distilled  with  superheated  steam;  when 
the  distillate  cools  and  solidifies,  the  olein  is  extracted  by  pressure. 
The  process  is  analagous  to  the  production  of  commercial  cottonseed- 
oil  and  lard  stearins  used  in  the  preparation  of  butterine,  lard  surro- 
gates, and  candles.  There  are  about  250,000  gallons  of  olein  available 
in  the  cotton  crop  of  the  United  States,  if  all  the  foots  were  used  for  the 
extraction  of  olein  and  none  used  for  the  manufacture  of  cheap  soaps. 

There  is  no  amount  of  animal  oils  or  fatty  refuse  available  for 
manufacturing  into  olein  that  can  in  any  material  way  affect  the 
broad  field  covered  by  linseed-oil  as  a  vehicle  for  paints. 

Chemistry  has  not  arrived  at  that  stage  of  development  where  the 
assembling  of  the  chemical  elements  of  fatty  substances  in  their  known 
proportions  will  produce  an  oil  or  fat.  All  such  substances  must  have 
a  natural  base  for  the  foundation  for  the  chain  of  operations  and 
reactions  necessary  to  change  their  nature. 

Lucol,  as  a  paint  vehicle,  therefore,  is  not  a  synthetical  com- 
pound, but  a  manufactured  paint  oil.  Its  endorsement  by  master 
painters  when  used  on  passenger-cars  or  other  works  which  are  cov- 
ered by  coatings  of  fossil-gum  varnish,  or  upon  ferric  bodies  which 
are  thoroughly  covered  with  rust,  is  no  evidence  of  its  resistance  to 
corrosion.  A  few  successful  applications  of  it  under  favorable  condi- 
tions will  not  counterbalance  the  failures.  Generally,  no  record  of 
the  failures  of  substitutes  for  linseed-oil  is  available  for  the  public,  who 
are  as  much  interested  in  knowing  what  not  to  use,  as  what  vehicle 
is  the  best  for  a  paint. 

A  siccative  oil  of  peculiar  properties  has  lately  been  introduced 
from  China  into  England  and  the  United  States.  Its  comparison 
with  linseed-oil  for  paint  and  varnish  coatings  is  as  follows: 

Chinese  wood-oil  *  has  thus  far  been  employed  for  the  manufacture 

*  "Uses  of  Chinese  Wood-oil  in  the  Manufacture  of  Paints  and  Varnishes." 
Translated  from  the  Fdrben  Zeitung,  by  the  Scientific  American,  January,  1895. 


252    SUBSTITUTES  FOR  LINSEED-OIL.     CHINESE  WOOD-OIL. 

of  lacquers,  varnishes,  and  paints,  on  account  of  its  peculiar  quality 
of  drying  thoroughly  in  about  6  to  8  hours.  Pigments  ground  in  the 
oil  furnish  excellent  paints,  that  do  not  remain  soft  and  sticky  below 
the  surface,  like  coatings  prepared  from  linseed-oil. 

Chinese  wood-oil  is  favorably  employed  as  a  floor  oil  or  paint  on 
account  of  its  hardness;  also  in  the  manufacture  of  an  oilcloth-like 
goods,  which,  when  dried  in  hot  air,  excel  the  ordinary  oilcloth  or 
water-proof  products  by  their  extraordinary  elasticity.  The  odor  of 
the  oil  is  very  peculiar,  resembling  lard,  and  remains  in  the  coating 
for  months,  and  even  for  years.  This  lard  odor  remains  in  the  lacquers 
made  from  the  oil;  hence  for  that  use,  also  for  floor  and  other  interior 
uses,  it  is  necessary  to  remove  it.  Disguising  the  smell  by  the  use  of  a 
volatile  oil  does  not  answer  the  purpose,  because  the  odor  reappears 
after  the  evaporation  of  it.  Among  the  remedies  resorted  to  are : 
Agitation  with  a  dilute  solution  of  permanganate  of  potassium ;  a 
filtered  solution  of  chloride  of  lime,  filtration  through  animal  char- 
coal; mixing  with  potato  flour,  also  storing  it  for  a  long  time  after 
filtration,  after  the  process  of  Bang  and  Ruffin.  It  is  also  possible 
to  obtain  a  tolerable  freedom  from  the  odor  by  the  use  of  a  blower 
passing  air  heated  to  not  exceeding  50°  C.  through  the  oil,  for  6  to  8 
hours,  when  it  loses  perceptibly  in  odor  and  can  be  used  for  lacquers 
or  floor-work.  For  outside  exposures  it  is  not  necessary  to  attach 
much  value  to  the  deodorization. 

Wood-oil  in  its  raw  state  dries  opaque,  probably  due  to  the  presence 
of  mucilage  and  albumin.  In  this  state  the  oil  becomes  waxy  at  low 
temperatures,  and  organic  salts  analogous  to  the  stearates  settle  out. 

Wood-oil  is  boiled  for  a  short  time  in  a  like  manner  to  linseed-oil 
with  a  small  percentage  of  red  lead  or  litharge,  else  it  will  always  remain 
opaque.  This  for  paints  is  immaterial,  but  boiling  is  necessary  to 
give  a  greater  drying  quality. 

In  boiling  the  oil,  whether  with  lead  or  manganic  compounds,  a 
temperature  of  200°  C.  must  not  be  exceeded,  otherwise,  in  the  use  of 
borate  of  manganese,  a  thickening  ensues,  followed  in  a  short  time  by 
complete  gelatination  and  waste  of  the  oil.  Heats  approximating 
160°  C.  and  in  any  case  not  over  180°  C.  should  only  be  used,  and  for 
but  a  short  time,  when  the  oil  should  be  removed  from  the  fire  and 
the  siccatives  stirred  in.  This  imparts  to  the  oil  a  drying  quality  and 
obviates  gelatination.  Pigments  can  be  ground  in  the  oil  as  usual 
with  the  use  of  linseed-oil.  Compositions  of  linseed-oil  and  wood-oil 
work  well  together,  being  especially  adapted  for  exterior  varnishes 


CHINESE  AND  JAPANESE  WOOD-OILS,  253 

on  account  of  the  hardness,  solidity  and  quick  drying  they  receive 
from  the  wood-oil,  and  the  elasticity  from  the  linseed-oil. 

The  important  drying  quality  renders  wood-oil  useful  in  the 
manufacture  of  fatty  lacquers.  It  cannot  be  employed  for  spirit 
lacquers,  as  it  is  insoluble  in  alcohol. 

The  wood-oil  of  China  and  Japan  is  obtained  from  the  seeds  of 
the  tung-oil  or  varnish  tree  (Aleurites  cordata,  Elaeococca  vernicia). 
Another  variety,  the  Aleurita  triloba,  furnishes  an  oil  of  less  drying 
power,  and  is  used  to  adulterate  the  oil  from  the  former. 

About  266,700,000  pounds  of  the  oil  are  annually  shipped  from 
Hankow  to  other  parts  of  China,  and  for  export.  The  Canton  wood- 
oil  is  said  to  be  better  and  purer  than  the  Hankow,  and  is  about  10 
per  cent  higher  in  price.  The  cost  of  these  oils  in  England,  where 
their  use  is  firmly  established,  is  from  4  to  4J  cents  per  pound. 

De  Negri  and  Sburlati  report  that  the  fruit  of  the  tree  from 
which  the  oil  is  extracted  contains  53.35  per  cent  of  oil,  42  per  cent 
being  recoverable. 

The  cold-pressed  oil  is  of  a  pale-yellow  color,  is  tasteless,  and  has  a 
smell  like  castor-oil.  The  hot-pressed  oil  is  a  medium  brown  in  color, 
with  a  taste  and  smell  like  hog  fat. 

The  drying  power  of  the  oil  is  superior  to  that  of  linseed-oil,  the 
cold-pressed  drying  better  than  the  hot-pressed. 

Its  specific  gravity  is  0.936  to  0.941.  Saponification  value,  156.6- 
172.  Iodine  value,  159-161  (de  Negri  and  Sburlati).  The  oil  is 
soluble  in  cold  absolute  alcohol  and  mixes  readily  with  linseed-oil. 
When  heated  with  litharge  it  turns  darker  in  color  and  evolves -a 
slight  smell  of  acrolein.  When  thinly  spread  on  glass  in  a  closed  room 
it  dries  to  a  whitish  film  resembling  milky  or  frosted  glass.  A  heavier 
coating  exposed  in  the  open  air  dries  in  about  6  hours.  The  oil  after 
heating  or  boiling  by  itself  develops  the  whitish  film,  but  when  boiled 
with  litharge  is  as  clear  and  bright  as  any  oil  varnish. 

Very  thick  layers  of  the  dried  oil  can  be  scraped  off  as  a  tough  mass 
quite  uniform  throughout.  It  has  an  exceptionally  small  adherence 
to  glass. 

The  balsam  known  as  wood-oil  or  gurjan  balsam,  from  the  Dip- 
terocarpus  turbinatus,  Gaertn,  should  not  be  confounded  with  the  tung- 
oils.  It  is  frequently  adulterated  by  them.  It  is  also  a  natural 
varnish. 


254  NATURAL  VARNISHES  OR  PAINT  OILS. 


Euphorbium. 

This  substance  is  in  its  experimental  stage  in  the  United  States 
as  a  vehicle  for  anti-corrosive  and  anti-fouling  paints.  Attention 
was  directed  to  its  anti-corrosive  qualities  as  a  natural  varnish  and 
its  probable  utility  as  a  vehicle  for  paints  about  the  year  1870,  from 
the  discovery  that  the  axes,  machetes,  and  other  tools  used  to  cut 
down  the  thickets  of  the  euphorbia  spurge,  to  clear  the  way  for  a 
surveying  expedition  in  Natal,  became  coated  with  a  strong  glutinous 
juice  that  adhered  so  firmly  to  them  as  to  be  with  difficulty  removed. 
The  tools  coated  with  it  did  not  rust  in  fresh  water,  and  bilge-water 
had  but  little  effect  upon  it.  When  articles  were  coated  with  it  and 
immersed  in  the  sea,  no  barnacles  or  marine  life  would  adhere  to  it. 
Its  effect  upon  insect  life  appeared  to  be  equally  repulsive,  and  timber 
coated  with  it  resisted  the  ravages  of  the  Teredo  navalis.  It  resists 
heat  and  cold  better  than  linseed-oil  and  varnish  vehicles,  while 
ammoniacal  and  chemical  vapors  do  not  cause  blistering,  scaling,  or 
other  injurious  action. 

Euphorbium  juice  has  a  strong  affinity  for  iron  and  steel,  and 
when  applied  in  its  crude  state  as  it  exudes  from  the  shrub,  has  no 
injurious  effect  upon  metals,  wood,  or  other  substances  used  for  engi- 
neering or  common  building  purposes.  When  prepared  for  a  paint, 
the  juice  undergoes  several  special  processes  and  becomes  a  clear 
gummy  vehicle  of  a  medium-brown  color,  that  receives  the  usual 
color  pigments  much  as  linseed-oil  does;  retaining,  however,  its  own 
protective  properties  unimpaired. 

Euphorbium,  prepared  for  a  vehicle,  appears  to  maintain  its 
properties  in  all  climates,  and  does  not  apparently  deteriorate  with  age. 
It  is  perfectly  elastic,  tenacious,  and  when  dry,  can  be  drawn  out  to  a 
thin  thread.  It  adheres  firmly  to  polished  steel,  tin  plate,  zinc  coat- 
ings, sheet  lead,  and  spelter.  Earth  acids  appear  to  have  little  effect 
upon  it,  as  pipes  coated  with  it  and  buried  for  a  number  of  years 
show  little  injury. 

Euphorbium  juice  has  a  bitter,  biting  taste,  is  very  acrid  and 
irritating  to  human  flesh,  corroding  and  ulcerating  the  body  wher- 
ever it  is  applied.  The  sores  resemble  those  from  nitric  acid,  and  are 
hard  to  heal.  In  this  and  nearly  all  other  respects  it  resembles  the 
crude  juice  gathered  from  the  Rhus  vemicifera,  called  by  the  Japanese 
urushi-naki,  the  native  lacquer-tree  of  Japan. 


NATURAL  VARNISHES.     EUPHORBIUM.  255 

The  euphorbium  of  commerce  is  imported  in  casks,  and  is  a  gummy, 
resinous  substance  in  the  form  of  drops  of  an  irregular  size  resembling 
gum  arabic.  The  drops  contain  vegetable  matter — twigs,  flowers, 
thorns,  etc.,  that  collect  on  the  gum  as  it  exudes  from  the  tree  and 
are  dried  in ;  though  many  of  the  tears  are  hollow  and  without  refuse 
in  them.  The  natural  color  of  the  tears  is  a  cloudy  pale  yellow  exter- 
nally, but  of  a  lighter  color  internally.  The  tears  break  easily  in  the 
fingers,  but  are  difficult  to  pulverize.  The  principal  part  of  the  process 
to  prepare  the  crude  gum  for  use  as  a  varnish  or  a  vehicle  for  paint  is 
to  free  it  from  the  vegetable  matter.  It  is  partially  dissolved  by 
water  and  almost  entirely  by  alcohol,  ether,  and  oil  of  turpentine.  Its 
composition  by  analysis  is,  viz.: 

A  resin  soluble     in  ether 26 . 95  per  cent. 

"     "      insoluble "      "     14 .25    "  " 

Euphorbin,  the  peculiar  principle 34.60    "  " 

Caoutchouc 1 . 10    "  " 

Malic  acids 1.50"  " 

Gum  salts 20 .40    "  " 

Ammonia  soluble  matters 1 . 20    "  " 


100.00    "      " 

It  has  no  acid  reaction  but  an  extremely  burning  taste. 

The  intense  acridity  is  due  to  the  resin,  soluble  in  the  ether,  which 
melts  at  107.6°  to  109.4°  F.  The  resin  insoluble  in  ether  melts  between 
246.4°  and  248°  F.  Euphorbin  is  a  crystallizable  substance,  fusing 
at  154.4°  F.,  and  soluble  in  ether,  benzine,  etc.,  but  not  in  hot  water. 

Euphorbium  dries  readily  without  the  use  of  metallic  salts  or 
solvent  driers.  Ox-gall  and  other  kindred  substances  appear  to  be 
the  best  driers  for  it,  when  any  are  required.  The  crude  resin  is  the 
product  of  the  Euphorbiacece:  the  genus  is  numerous.  There  are  about 
600  species,  many  of  which  are  natives  of  nearly  every  country  in 
the  temperate  zones,  and  are  commonly  known  as  spurgeworts. 

The  euphorbium  spurge,  or  E.  resinifera,  is  a  shrubby  and  herba- 
ceous succulent,  frequently  covered  with  thorns  and  having  stalks  from 
3  to  6  and  sometimes  10  feet  in  height,  and  grows  in  almost  impene- 
trable thickets  in  the  hot  interior  deserts  of  Morocco  and  other  hot 
climates.  Euphorbium  is  obtained  from  the  incisions  made  on  the 
plant;  the  corrosive  milky  liquid  hardens  on  the  stems  in  resinous 
drops  or  tears,  or  like  spruce-gum  deposits,  and  is  collected  in  various 
ways. 

The  commercial  supply  comes  principally  from  the  southern  prov- 


256  NATURAL   VARNISHES.     EUPHORBIA. 

inces  of  Morocco,  in  the  districts  of  Aitaitab  and  Juteefa,  at  the  foot 
of  the  lower  range  of  the  Atlas  Mountains. 

The  euphorbium  gum  from  Natal  is  considered  to  be  inferior  to 
the  Morocco  product.  North  Africa  is  capable  of  producing  euphor- 
bium in  sufficient  amounts  to  supply  almost  any  demand  for  it. 

The  gum  is  called  in  Arabia  "Darkmows,"  and  is  known  in  the 
Eastern  markets  as  "Farfium." 

In  India  there  are  116  species  of  the  Anacardiacece  referred  to  23 
genera,  in  addition  to  the  E.  resinifera  and  some  other  varieties  found 
in  Arabia. 

The  E.  dracunculoides  in  India  (jy-chee)  yields  25  per  cent  of 
a  clear  oil  of  a  yellowish  or  greenish-yellow  color  from  the  dry 
husked  seed.  The  oil  is  more  limpid  than  linseed-oil,  does  not 
become  ropy  from  age,  and  is  used  for  a  burning  and  drying  oil. 

The  E.  lathyris  is  raised  on  the  edges  of  the  fields  in  France, 
Germany,  and  Switzerland.  It  contains  40  per  cent  of  a  fluid  oil  of  a 
siccative  nature. 

The  E.  neriifolia  grows  wild  in  Burma,  Baluchistan,  the  Malay 
Islands,  etc.  It  yields  a  gum  of  a  gutta-percha  nature  on  boiling 
the  stems  and  twigs  of  the  shrub. 

The  E.  Royleana  is  a  large  fleshy  shrub  common  on  the  dry  rocky 
hillsides  of  the  Himalayas,  growing  at  an  elevation  of  6000  feet.  The 
sap  of  this  plant  yields  a  superior  gutta-percha. 

The  Pisticia  Lentiscus  yields  the  resin  mastic. 

The  Melanorshoea  usitatissima  yields  the  black  varnish  of  Burma. 

The  Indian  Holigarna  longifolia  also  yields  a  varnish. 

The  Indian  Odina  Wodier  is  covered  with  its  brown  gum,  which 
streaks  down  the  stem  and  ultimately  turns  black. 

The  E.  pulcherrima  is  an  ornamental  shrub  grown  in  Mexico  that 
yields  a  milky  sap  which  hardens  into  a  black  gum,  and  can  be  boiled 
down  to  a  sort  of  gutta-percha.  Guatemala  and  other  countries  near 
the  torrid  zone  also  have  a  large  number  of  trees  that  furnish  the 
natural  varnishes,  though  no  attempt  has  been  made  to  bring  them 
into  commercial  importance. 

The  P.  terebinthus  is  a  tree  growing  along  the  shores  of  the  Medi- 
terranean Sea.  It  furnishes  the  Cyprus  turpentine. 

The  Japanese  lacquer-tree,  or  the  urushi-naki,  is  known  in  China 
as  the  Tsi-chou.  It  belongs  to  the  botanical  order  of  Anacardiacece, 
to  which  also  belongs  the  Rhus  vernicifera,  a  tree  with  very  long,  glossy 
leaves  resembling  those  of  the  ordinary  sumach,  poison-oak,  dog- 


NATURAL  VARNISHES.    JAPANESE  LACQUER.  257 

wood,  ivy,  etc.  The  American  dogwood  was  formerly  thought  to 
be  of  the  same  species,  but  is  now  placed  in  another  of  the  same  order. 

In  Japan  *  the  lacquer-tree  grows  to  the  height  of  about  30  feet, 
and  at  the  age  of  40  years  is  about  40  inches  in  diameter.  It  reaches 
its  greatest  perfection  in  the  yield  and  quality  of  the  lac  or  varnish 
at  the  age  of  18  years. 

The  crude  lac,  called  ki-urushi,  is  collected  at  any  time  between 
the  months  of  April  and  October  by  making  a  number  of  horizontal 
incisions  in  the  bark  of  the  tree  in  a  manner  similar  to  the  "boxing" 
practised  to  gather  the  sap  of  the  long-leaf  pine-  or  turpentine-tree. 
The  tree  is  hacked  in  this  manner  for  from  60  to  80  days,  or  until  it 
dies,  when  it  is  cut  down,  the  bark  and  sap-wood  removed  and  steeped 
in  hot  water,  which  extracts  the  last  remnant  of  the  lac,  about  half  a 
pint,  which  forms  the  poorest  quality  of  lac,  known  as  "roiro-urushi," 
or  black  varnish.  The  tree  seldom  survives  the  first  season's  hack- 
ing, at  whatever  age  it  is  done. 

The  varnish-tree  is  probably  native  to  China,  but  it  is  also  found 
native  in  Japan,  and  is  cultivated  all  over  Nippon  and  in  several 
districts  of  Kiushia  and  Shikoku,  and  there  are  extensive  planta- 
tions in  the  valley  of  Tadamigawa  and  Northern  Echigo.  A  tem- 
perate climate  seems  to  best  suit  the  growth  of  the  tree,  as  it  reaches 
its  greatest  perfection  on  the  main  island  north  of  latitude  36°.  It 
is  cultivated  in  Northern  Hondo,  between  37°  and  39°.  It  may  be 
of  interest  in  considering  the  question  of  habitat  to  note  that  the 
Rhus  vernicifera,  mentioned  by  Mr.  J.  J.  Rein,  are  growing  in  Ger- 
many at  Frankfort-on-Main  and  at  Strasburg.  They  endured  the 
hard  winter  of  1879-80,  when  the  temperature  reached  27°  C. 
In  Japan  the  lowest  temperature  in  Northern  Nonshiu  is  — 12°  C. 

The  lac  is  purified  by  straining  it  through  cotton  cloth,  evapo- 
rating the  water  by  exposure  to  the  sun  or  by  a  gentle  heat.  Some- 
times water  is  added  to  the  crude  lac,  and  they  are  ground  together 
on  a  paint  slab,  and  then  the  water  is  evaporated.  Various  coloring 
matters  are  added  to  the  purified  lac  by  grinding,  as  is  usual  in  the 
manufacture  of  oil  paints.  Black  lacquer  other  than  that  furnished 
from  the  last  run  of  sap  is  produced  by  the  addition  of  some  salt  of 
iron. 

*  Excerpts  from  "Japanese  Lacquer  and  the  Varnish-tree  that  produces  it." 
A  communication  to  the  author  from  the  Bureau  of  Forestry,  United  States 
Department  of  Agriculture.  By  Geo.  B.  Ludworth,  Chief  of  Division  of  Forestry 
Investigation,  June,  1902. 


258  NATURAL  VARNISHES.    JAPANESE  LACQUER. 

Whenever  driers  are  required,  a  little  oil  of  tea  is  used,  also  the 
gall  from  pigs  and  oxen,  to  give  body  to  the  lac.  The  purest  lac  is 
from  the  first  run  of  the  sap  after  tapping.  It  is  called  nashyi-urushi, 
and  is  bleached  in  shallow  vessels  laid  in  the  sunlight.  The  other  prin- 
cipal grades  are  the  henki-urushi,  the  unbleached  jeshimi-urushi,  and 
the  roiro-urushi,  or  black  varnish. 

There  are  about  20  different  grades  and  qualities  of  these  lacquers 
in  the  Japanese  market,  of  which  the  above  are  the  principal  ones. 
They  vary  in  color  from  a  light  brown  to  a  deep  jetty  black. 

Lacquer  is  thinned  only  by  heating.  The  addition  of  water 
thickens  the  lac  into  a  jelly.  Lacquered  objects  are  always  hardened 
in  a  humid  atmosphere,  such  as  a  room  with  wet  cloths  hung  on  the 
walls,  or  containing  a  spray  or  vessels  of  water. 

All  varieties  of  varnish-trees  are  propagated  by  the  seeds  and 
cuttings.  The  seeds  are  gathered  in  October  and  sown  early  in  the 
spring,,  make  10  to  12  inches'  growth  the  first  season,  and  in  10 
years  are  9  to  10  feet  high  and  from  2  to  3  inches  in  diameter.  In  a 
favorable  soil  the  annual  height-growth  during  the  first  6  years  is  from 
20  to  30  inches,  and  diminishes  afterward  to  from  10  to  20  inches. 
Plants  from  root  cuttings  grow  more  rapidly  than  seedlings,  but  the 
latter  make  hardier  and  longer-lived  trees.  The  trees  after  the  first 
5  or  6  years  require  very  little  care,  and  are  generally  tapped  at  any 
period  after  the  tenth  year  of  their  growth,  though  sometimes  it  is 
done  when  only  4  or  5  years  old. 

The  climate  and  soil  of  at  least  one-third  of  the  United  States 
are  as  favorable  for  the  growth  of  lacquer-trees  as  those  of  Japan  or 
China.  Their  cultivation  requires  no  more  care  than  that  given 
to  the  sugar-maple  or  the  Eucalyptus.  Specimens  of  the  trees  are 
growing  in  the  grounds  of  the  Department  of  Agriculture  at  Wash- 
ington, D.  C. 

Plants  which  are  largely  cultivated  in  Europe  have  been  confused 
with  the  Japanese  Rhus  vernicifera.  They  are,  however,  a  differ- 
ent variety  of  the  tree.  The  Ailanthus  glandulosa  Desf.,  in  France 
called  Verms  de  Japan,  is  also  of  the  varnish-bearing  species. 

The  poison  -  sumach,  Rhus  verneata,  common  in  the  Eastern 
United  States,  yields  a  sap  that  furnishes  a  black,  lustrous,  durable 
varnish,  very  similar  to  that  derived  from  the  Japanese  tree. 

Other  trees  that  belong  to  the  same  botanical  order  (Anacardiacece) 
that  yield  natural  varnishes  have  been  referred  to  in  the  article 


NATURAL   VARNISHES.     CHINESE  LACQUER.  259 

"Euphorbium."  None  of  the  Indian  varnish- trees  west  of  the  Ganges 
yield  as  white  or  pure  a  lacquer  as  those  in  China  or  Japan. 

A  species  of  varnish-tree  that  grows  in  India  was  thought  to  be  the 
veritable  Anacarde,  but  it  is  entirely  different  from  the  Japanese 
"urusi"  variety. 

No  attempt  to  cultivate  any  of  the  varnish-trees  on  a  commercial 
scale  has  been  made  in  either  Europe  or  America.  The  manufacture 
of  lacquer  and  lacquer-ware  is  one  of  the  most  important  industries 
of  China  and  Japan.  It  seems  natural  that  if  the  largest  users  of 
varnish  in  the  world  depend  almost  solely  upon  these  natural  products, 
their  cultivation  in  America  is  well  worth  trying. 

-In  China  the  Rhus  vernicifera,  or  varnish-tree,  is  called  Ch'i-shu 
(Tsi-chou),  also  Li-tschi.  It  grows  wild  in  the  province  of  Fingo 
and  on  the  island  of  Tricom,  and  is  cultivated  in  the  mountains  of 
Hupeh  and  Seechwan,  but  the  best  varieties  are  found  in  the  province 
of  Jamatto,  where  it  is  cultivated  extensively.  It  is  probable  that 
the  Mingpo  and  Foochow  varnishes,  as  well  as  the  Hupeh,  are  from 
the  Rhus  vernicifera  A  varnish-tree  growing  in  South  China  differs 
from  the  above  variety,  but  is  not  well  known  at  present. 

In  China  the  Rhus  vernicifera  grows  about  15  to  20  feet  in  height, 
seldom  reaching  one  foot  in  diameter,  and  has  but  few  branches. 
The  bark  is  white,  knotty,  and  peels  readily.  The  wood  is  fragile, 
resembling  the  willow;  the  pith  is  very  abundant.  Its  leaves  have  a 
mild  taste,  and  when  rubbed  on  paper,  dye  it  a  dull  black.  The  flowers 
are  greenish  yellow,  and  have  an  odor  resembling  orange-blossoms. 
The  fruit  is  of  the  size  and  shape  of  chick-pea,  and  at  its  maturity  is 
very  hard  and  of  a  dirty  color.  The  seed  furnishes  an  oil  and  wax 
which  are  extensively  used. 

From  the  berries  of  the  Rhus  vernicifera,  Rhus  succedaba,  and 
other  related  Chinese  and  Japanese  species,  a  vegetable  tallow  is 
extracted  and  used  for  candles.  The  wax  is  exported  in  large  quan- 
tities to  Great  Britain  and  the  United  States  for  an  adulterant  or 
substitute  for  beeswax. 

The  general  composition  of  crude  lac  is  lac  acid  (a  resinous  acid, 
soluble  in  ether),  60  to  80  per  cent,  a  gum  3  to  6  per  cent,  a  nitrog- 
eneous  substance  resembling  albumin  1.7  to  3.5  per  cent  of  a  volatile 
acid,  and  water,  which  are  driven  off  in  the  preparation  of  refined 
lacquer.  The  color  of  the  lacquer  is  a  light  yellow  or  brown,  according 
to  the  season  in  which  the  tree  is  tapped. 

The  Chinese  crude  lac  is  collected  and  purified  in  the  same  way 


260  NATURAL  VARNISHES.     CHINESE  LACQUER. 

as  in  Japan.  In  both  of  the  processes  for  its  collection  and  refining 
great  care  is  necessary.  The  poisonous  element  in  the  lac,  whether 
inhaled  or  in  contact  with  the  flesh,  produces  what  are  known  as 
varnish  boils,  accompanied  by  an  intolerable  itching  and  burning 
sensation,  similar  to  that  produced  by  the  poison-ivy.  They  are 
difficult  to  heal,  and  resemble  the  effect  of  nitric  acid  on  the  flesh. 

The  Chinese  and  Japanese  use  lacquer  as  a  varnish  or  vehicle 
for  colors  on  all  kinds  of  household  utensils,  also  for  the  inside  and 
outside  coatings  on  their  buildings.  Lacquer  as  a  vehicle  can 
be  used  for  all  colors  except  a  pure  white  and  some  of  the  lighter 
shades  of  other  colors.  It  is  applied  to  wood,  porcelain,  and  metals, 
and  forms  a  hard  resinous  surface,  highly  lustrous,  practically  insolu- 
ble in  boiling  water,  alcoholic  liquids,  alkaline  and  acid  solutions,  unless 
in  a  highly  concentrated  form.  Applications  of  lacquer  to  the  under- 
water surfaces  of  a  number  of  Japanese  war  vessels  for  both  anti-cor- 
rosive and  anti-fouling  coatings  have  been  very  successful.  The 
coatings,  after  a  sea-duty  of  four  years  of  the  vessels  to  which  they 
were  applied,  showed  no  signs  of  either  fouling  or  corrosion. 
Applications  of  other  anti-fouling  paints  of  all  characters  over 
lacquer  coatings  were  failures,  the  urushic  acid  of  the  lacquer  attack- 
ing the  metallic  base  of  the  foreign  anti-fouling  paint,  resulting 
practically  in  the  destruction  of  both. 

The  best  results  for  under-water  marine  work  with  lacquer  is  had 
when  the  first  coating  is  a  heavy  one  and  almost  pure  lacquer.  The 
succeeding  coats  can  be  thinner  in  body  and  contain  either  a  pigment 
or  some  inert  substance  to  give  body.  Mica,  graphite,  lampblack, 
etc.,  have  been  used  experimentally  with  success  for  these  secondary 
coatings. 


CHAPTER  XXVII. 

DECAY   OF    PAINT. 

RUST  proceeds  solely  from  the  action  of  an  acidulated  moisture 
upon  a  bright  or  clean  iron  surface,  and  is  probably  only  a  point 
at  its  inaugural.  The  affinity  of  the  iron  for  the  oxygen  in  the  acidu- 
lated moisture  of  the  air  or  water  in  the  oil,  or  from  other  sources, 
is  greater  than  its  bond  with  the  hydrogen  as  water  (H2O),  the  decom- 
position ensuing  releases  the  hydrogen,  which  is  sixteen  times  the 
volume  of  oxygen  united  with  the  iron  to  form  hydrated  Fe2O3  or  red 
rust.  The  hydrogen,  from  its  light  specific  gravity,  in  its  effort  to 
escape  into  the  air  pushes  up  the  overlying  paint  coating,  increases 
the  area  of  the  affected  part,  cracks  the  coating  in  its  exit,  moisture 
enters  again,  and  corrosion  is  master  of  that  location.  The  rust 
which  has  thus  been  formed  is  hygroscopic  and  carries  24  per  cent 
of  moisture  as  it  forms.  This  moisture  never  dries  out  under  any 
atmospheric  heat  conditions,  but  is  ever  ready  for  a  chemical  decom- 
position; the  hydrated  red  rust,  being  nearly  two  times  the  volume 
of  the  iron  from  which  it  is  formed,  adds  its  efforts  to  the  free  hydrogen 
to  push  up  the  coating  and  form  a  blister  and  crack  in  the  coating. 
How  energetic  this  mechanical  action  due  to  corrosion  is,  may  be 
observed  on  the  ordinary  cast-iron  hand  railings  for  fences  and  out- 
side steps  of  New  York  City  and  other  city  houses,  which  in  hundreds 
of  instances  are  split  for  more  or  less  of  their  length.  Cast-iron 
water  or  gas-pipes,  with  bell  and  spigot  joints,  are  frequently  made 
with  rust  joints.  They  almost  invariably  burst  the  bells  by  the  swell- 
ing of  the  iron  cement  used  to  make  the  joint. 

The  cut,  Fig.  35,  shows  a  section  of  a  well-known  railway  viaduct, 
the  iron  construction  having  been  painted  over  mill-scale,  or  in  the 
condition  the  material  left  the  rolling-mill  and  workshop.  It  had 
received  the  usual  treatment  given  by  contracting  engineers  to  remove 
the  mill-scale  preliminary  to  painting. 

Many  sections  of  the  New  York  City  and  other  elevated  rail- 
ways, also  the  Brooklyn  Suspension  Bridge  trusses  show  mill-scale 

261 


262 


DECAY   OF  PAINT.     MILL-SCALE  CORROSION. 


corrosion  to  an  equal  extent.     Fig.  36  shows  the  mill-scale  corrosion 
on  one  of  hundreds  of  New  York   elevated  railway  columns,  orig- 


FIG.  35. 


FIG.  36. — Mill-scale  corrosion,  Phoenix  column. 

inally  painted  with  red   lead.      The  corrosion    now  in   progress   is 
strong  enough  to  break  through  and  cast  off  six  or  more  paint  coat- 


DECAY   OF  PAINT.     MILL-SCALE  CORROSION.  263 

ings  that  have  been  applied  over  the  red  lead  since  the  columns 
were  placed  in  position. 

The  corrosion  existing  in  BrunelPs*  tubular  iron  bridge  over  the 
St.  Lawrence  River  at  Montreal,  Canada,  had  proceeded  to  so  great 
an  extent  as  to  require  the  removal  of  the  whole  structure,  it  being 
impossible  to  repair  it.  The  efforts  to  replace  the  cross  floor-beams 
supporting  the  rail  stringers  resulted  in  loosening  every  rivet  in  the 
neighborhood  of  the  repairs.  Pitting  around  the  heads  of  the  rivets 
had  proceeded  so  far  and  deep  that  it  was  impossible  to  cut  them 
out  without  loosening  every  contiguous  rivet. 

This  bridge  had  been  kept  well  painted  with  iron-oxide  and  some 
experimental  paints  applied  coat  after  coat.  These  coatings  when- 
ever removed,  or  that  fell  off  during  the  periodical  clean-up,  or  attempts 
to  repair  and  paint  the  structure,  showed  the  several  coatings  of  mill- 
scale,  paint,  and  new  rust  formations  as  plainly  arranged  as  the  leaves 
of  a  book. 

Fig.  37  shows  a  similar  state  of  corrosion. 


FIG.  37. — Corrosion  of  steel  girder,  Washington  Street  railway  bridge,  Boston, 

Mass. 

In  1879,  Sir  Nathan  Barnaby  stated  as  the  result  of  his  obser- 
vations of  ships'  metal  in  the  English  naval  stations,  that  when  the 
mill-scale  was  left  upon  the  plates,  angles,  and  other  parts  of  the 
ship,  its  effect  upon  the  neighboring  bared  metal  was  as  strong  and 
continuous  as  copper  would  be. 

*  Transactions  American  Society  Mechanical  Engineers,  Vol.  XV,  1894, 
paper  number  626,  p.  410. 


264  DECAY  OF  PAINT.    MILL-SCALE  CORROSION. 

In  1887,  Mr.  Rialton  Dixon  gave  before  the  Institute  of  Naval 
Architects  his  experience  as  to  a  vessel  built  entirely  of  steel  some 
eight  years  before,  which  was  found  to  be  greatly  corroded  in  the 
bunkers  and  water-ballast  chambers  near  the  engine  room  and  boilers. 
Some  of  the  angle-irons  had  entirely  disappeared,  and  the  tie-plates 
were  eaten  away  in  holes.  This  action  could  be  traced  directly  to  the 
presence  of  mill-scale,  and  whether  the  surfaces  were  coated  with 
paint  or  cement  or  not,  the  corrosion  was  always  present  upon  those 
plates  and  angles  that  had  mill-scale  upon  them,  and  was  absent  in 
those  free  from  it.  The  presence  of  the  paint  or  other  coating  retarded 
corrosion  only  in  a  minor  degree  by  preventing  moisture  from  reach- 
ing the  metal  covered  by  the  mill-scale. 

In  1882  Mr.  Farquharson,  on  behalf  of  the  English  Board  of 
Admiralty,  conducted  a  number  of  very  exhaustive  experiments  at 
the  different  naval  stations  to  test  the  action  of  mill-scale  on  ships' 
metal.  The  result  was  to  establish  beyond  dispute  that,  first, 
no  pitting  occurred  on  mild  steel  when  freed  from  mill-scale;  second, 
that  the  loss  in  weight  from  corrosion  of  clean  mild  steel  and  clean 
iron  did  not  differ  much;  third,  that  the  action  of  mill-scale  is  con- 
siderable and  continuous,  and  equal  to  a  similar  amount  of  copper  in 
its  corrosive  action  on  metal  covered  by  it.  Since  these  experiments 
the  Admiralty  have  never  wavered  in  their  practice  of  having  all 
of  the  ships'  metal  pickled  to  remove  the  mill-scale,  whether  it  is 
to  be  covered  by  paint  or  cement,  or  to  be  galvanized. 

Destructive  Agents  of  Paints. 

Pure  water  is  a  greater  destructive  element  to  an  oil  coating 
than  solutions  of  sal  ammoniac,  chloride  of  magnesium,  common 
salt,  or  natural  sea-water,  if  free  from  sewage,  all  of  which  are  agents 
of  destruction.  The  decay  of  a  paint  is  hastened  by  mechanical  action 
if  the  water,  either  fresh  or  salt,  or  the  other  solutions,  are  in  motion. 
Ordinary  commercial  oil  coatings  are  destroyed  by  diluted  muriatic 
and  nitric  acids,  alkaline  liquors,  ammonia,  sulphide  of  ammonium, 
soda,  caustic  alkalies,  and  alkaline  solutions  of  coal  ashes,  clinkers, 
cinders,  soot,  etc.  Diluted  sulphuric  acid  does  not  materially  affect 
an  oil  coating.  All  gaseous  acids  destroy  the  coating  quicker  than 
the  acids  in  diluted  aqueous  solution,  the  destruction  being  in  all 
cases  hastened  by  heat  or  motion.  Hence,  to  determine  the  probable 
protective  value  of  any  paint  or  other  coating,  it  is  necessary  to  know 
the  detrimental  influences  to  which  it  is  to  be  subjected. 


DECAY  OF  PAINT.  265 

Changes  in  Paint  Coatings. 

A  coating  of  paint  appears  to  be  a  very  simple  thing,  as  it  is,  when 
applied  to  a  house  or  barn  and  both  are  left  to  their  fate,  but  when 
applied  to  an  important  engineering  structure,  with  all  the  vicissi- 
tudes of  service  in  the  extremes  of  heat  and  cold,  sunshine  and  storm, 
atmospheric  and  other  gases  from  natural  or  manufacturing  sources, 
from  corrosive  liquids  and  solids,  it  is  a  different  matter,  and  requires 
more  engineering  experience  to  select,  more  chemical  knowledge  to 
compound,  and  more  technical  details  to  get  the  right  thing  in  the  right 
place  at  the  right  time,  in  the  right  manner,  and  in  the  right  amount 
than  the  general  run  of  master  painters  do  or  can  give  to  the  subject. 
If  the  influence^  to  which  a  coating  of  paint  is  to  be  subjected  are 
known,  it  can  generally  be  determined  in  advance  whether  it  will 
be  durable.  For  instance,  zinc  white  or  oxide  (ZnO,  specific  gravity, 
5.42)  applied  as  an  external  coating  absorbs  carbonic  acid  from  the 
air  and  some  moisture,  changing  to  a  carbonate  of  zinc  (ZnCO3, 
specific  gravity,  4.44).  During  this  change  there  is  an  increase  in 
volume  from  14.9,  as  an  oxide,  to  28.1  as  a  carbonate.  This  change 
from  an  oxide  to  a  carbonate  is  a  chemical  one,  and  occurs  during 
the  process  of  drying,  but  the  change  in  the  volume  of  the  two  substances 
exerts  a  mechanical  action  also  in  the  atoms  of  the  pigment,  not  only 
to  disrupt  them  and  leave  them  loose  and  easily  carried  away  by 
the  wind,  rain,  etc.,  but  cracks  and  loosens  the  oil  vehicle  in  which  the 
pigment  is  embedded  as  well  as  its  bond  to  whatever  surface  it  covers 
But  if  the  zinc-oxide  coating  is  applied  in  a  closed  room,  though  the 
air  contains  the  same  amount  of  carbonic  acid,  or  even  more  than 
the  external  air,  the  oxide  does  not  change  to  a  carbonate,  as  the 
necessary  moisture  is  lacking;  hence  zinc  oxide  for  internal  coatings 
is  durable,  but  for  outside  coatings  is  perishable. 

Red  lead  (Pb304,  specific  gravity,  9.07)  remains  unchanged  under 
ordinary  atmospheric  conditions,  but  if  the  air  contains  hydric  sul- 
phide, as  it  does  in  many  manufacturing  establishments  and  towns, 
to  a  notable  extent,  it  will  by  an  inexorable  chemical  law  change 
the  oxide  to  a  sulphide  of  lead  (PbS,  specific  gravity,  7.13),  and 
this  chemical  change  (usually  denoted  by  the  blackening  or  discolora- 
tion of  the  coat)  will  also  be  accompanied  by  an  increase  in  volume 
of  the  sulphide  of  about  22  per  cent,  this  increase  acting  mechanically 
to  disturb  the  bond  between  the  pigment  vehicle  and  surface  coated. 

The  addition  of  carbonate  of  lime  (chalk)  to  an  iron-oxide  pig- 


266  DECAY  OF  PAINT. 

meat,  whether  made  from  the  iron  ore,  or  from  calcined  copperas 
(FeSO47H20),  to  neutralize  the  sulphuric  acid  developed  in  the  cal- 
cination of  the  copperas  or  roasting  of  the  ore  (as  heretofore  noted), 
is  another  instance  in  which  an  inexorable  chemical  change  in  one 
of  the  pigment's  loose  substances  is  accompanied  by  a  change  in  us 
specific  gravity,  its  corresponding  change  in  volume,  and  a  mechan- 
ical action  to  reinforce  the  chemical  action  due  to  the  raw-oil  vehicle 
loaded  with  its  charge  of  driers,  whose  function  is  to  either  decom- 
pose or  consume  by  a  slow  combustion  the  "mucosities"  in  the  oil 
while  attempting  to  dry.  All  these  instances  are  similar  in  effect 
to  what  would  occur  in  the  plastered  wall  of  a  building  if  the  mortar 
used  in  it,  when  partially  dry,  should  begin  to  increase  in  volume 
to  the  amounts  as  given  above.  Other  instances  could  be  cited,  but 
these  show  that  the  pigments  of  the  coating  can  be  so  chosen  as  to 
preclude  the  destruction  by  them  of  the  coating,  but  that  it  is  almost 
impossible  to  guard  the  vehicle  from  the  injurious  influences  inherent 
in  the  composition  of  the  pigment,  that  is  changed  in  character,  after 
its  application,  by  chemical  laws.  Hence  the  absolute  necessity 
that  an  order  for  a  protective  paint  should  include  the  conditions 
it  is  to  be  subjected  to. 

In  addition  to  the  preceding  remarks  upon  iron  oxide,  graphite, 
and  other  paints,  and  the  several  tests  given  in  detail  of  a  few  of 
the  many  paint  compounds,  it  may  be  noted,  viz.: 

All  pigments  *  can  be  grouped  into  three  classes,  according  to  their 
affinity  for  linseed-oil. 

First.  Those  that  form  chemical  combinations  called  soaps  and 
are  generally  the  most  durable.  They  consist  of  lead,  zinc,  and 
iron  bases,  of  which  red  lead  combines  with  the  oil  to  the  greatest 
extent;  next,  the  pure  carbonate  white  lead  made  by  the  "Old  Dutch 
Process,"  followed  by  zinc  oxide  and  iron  oxide,  Turkey  umber,  yellow 
ochre ;  also,  faintly,  the  chromates  of  lead,  chrome-green,  and  chrome- 
yellow. 

Second.  Pigments  of  this  class,  being  neutral,  have  no  chemical 
affinity  for  the  oil;  they  need  large  amounts  of  driers,  either  com- 
bined with  and  carried  by  the  oil,  or  as  free  driers.  They  include 
all  blacks,  graphites,  slates,  slags,  vermilions,  Prussian,  Paris,  and 
Chinese  blues,  terra  de  sienna,  Vandyke  brown,  Paris  green,  verdigris, 
ultramarine,  carmine,  and  madder  lakes.  The  last  seven  are  trans- 

*  "  Pigments."     English  Encyclopedia  of  Painting,  1880. 


CATALYSIS  IN   THE  DECAY  OF  PAINT.  267 

parent  colors,  and  are  better  adapted  for  varnish  mixtures  and  glazing. 

Third.  Pigments  of  this  class  act  destructively  to  linseed-oil. 
They  have  an  acid  base  (mostly  tin  salt,  hydrochloride  of  tin,  and 
redwood  dye)  which  forms,  with  the  albuminous  and  gelatinous 
matters  in  the  oil,  a  jelly-like  compound  that  does  not  work  well  under 
the  brush  nor  harden  sufficiently,  and  can  be  used  in  a  varnish  for 
glazing  only.  Among  the  most  troublesome  are  the  lower  grades 
of  so-called  carmines,  madder  lakes,  rose-pinks,  etc.,  which  contain 
more  or  less  acidulous  dyes,  forming  with  linseed-oil  a  soft  paint, 
that  dries  on  the  surface  only  and  can  be  peeled  off  like  the  skin  of 
ripe  fruit. 

"Catalysis  "  is  a  term  introduced  by  Berzelius,  and  by  him  applied 
to  the  changes  that  sugar  solutions  undergo  in  the  process  of  fer- 
mentation, and  now  used  to  denote  the  changes  that  certain  substances, 
by  their  mere  presence,  effect  in  other  bodies  without  themselves 
undergoing  any  apparent  change.  Catalytic  action  is  a  potential 
agent  in  the  decay  of  paint  coatings,  and  manifestly  has  not  received 
the  attention  from  paint  chemists  and  compounders  that  its  marked 
action  on  the  life  of  a  coating  warrants.  The  present  efficiency  of 
the  incandescent  gaslight  is  wholly  due  to  catalytic  action  between 
the  substances  that  compose  the  mantle  when  excited  by  the  com- 
bustion of  the  gas.  In  the  development  of  this  light  all  of  the  rare 
mineral  oxides  and  metals  and  the  oxides  of  the  baser  metals,  chro- 
mium, alumina,  cobalt,  manganese,  nickel,  and  iron,  when  associated 
with  thoria  in  the  mantle,  have  been  found  to  act  as  catalytic  agents 
to  carry,  condense,  or  absorb  oxygen,  that  increases  the  flame  tem- 
perature of  the  mantle  and  consequently  increases  the  light.  This 
flame  temperature  in  some  cases  reaches  the  point  where  volatiliza- 
tion of  some  of  the  baser  metals  and  oxides  ensues.  Charcoal,  pow- 
dered glass,  porcelain,  flour  spar,  crystallized  quartz,  pumice-stone, 
and  other  kindred  substances  are  also  found  to  act  as  catalytic  agents 
in  combustion,  but  do  not  develop  so  high  a  flame  temperature  in 
the  mantle  as  the  other  substances  above  noted. 

Combustion  of  any  substance  may  be  quick  and  attended  by  a 
high  temperature,  as  in  the  case  of  the  incandescent  gaslight,  or  it 
may  be  of  low  temperature  and  extend  over  years  of  time,  but  the 
amount  of  heat  evolved  from  the  destruction  of  the  substance  and 
the  resultant  products  of  combustion,  or  decomposition,  are  the 
same  in  all  cases,  even  if  the  physical  effects  are  apparently  different. 

Nearly  every  substance  in  a  paint  coating  has  been  found  to  be 


268  CATALYSIS   IN   THE  DECAY  OF  PAINT. 

catalytic  to  some  other  substance,  either  in  its  own  class  as  a  so-called 
inert  mineral  pigment,  or  in  the  chemical  class  of  oxides  having  a  lead, 
zinc,  iron,  or  other  metallic  base.  Individually,  they  may  be  appar- 
ently unaffected  by  long  exposure  to  the  air  while  in  their  loose  state 
or  in  packages  or  bulk;  but  when  mixed  together,  they  take  up  moist- 
ure or  oxygen  to  a  greater  or  less  degree,  either  by  absorption  in 
mass  or  by  condensation  upon  their  surfaces,  and  catalytic  action 
ensues.  The  oil  vehicle  and  driers  are  catalytic  of  themselves,  and 
when  mixed  with  the  pigments  act  more  energetically  as  carriers 
of  oxygen  even  when  the  coating  is  apparently  dry.  In  all  pigments 
and  vehicles,  the  one  that  is  the  most  refractory,  or  that  is  the  most 
resistant  to  oxidation  in  whatever  form  the  oxygen  may  be  presented, 
is  the  one  that  acts  the  part  of  the  thoria  in  the  gaslight  mantle, 
becoming  the  negative  or  non-consumable  substance,  that,  though 
excited  to  a  greater  activity  by  the  presence  of  the  other  substances 
in  the  paint  compound,  retains  its  resistance  to  a  change  the  longest 
at  the  expense  of  the  other  associated  substances.  Thus  far,  lamp- 
black and  graphite,  in  their  subdivided  form  as  pigments,  appear 
to  be  the  only  substances  not  subject  to  catalytic  action,  or  if  it  is 
present  it  is  so  weak  that  the  life  of  the  coating  is  not  materially 
affected  from  this  cause.* 

Caustic  Action  of  Mortar  upon  Paint. 

An  examination  (1901)  of  iron  floor-beams  taken  out  after  an 
exposure  of  about  forty  years  showed  that  the  beams  originally 
were  particularly  well  painted  and  laid  in  a  location  where  only 
the  dry  warm  atmosphere  of  a  residence  reached  them.  The  paint 
coatings  had  been  thoroughly  destroyed  by  the  caustic  action  of 
the  lime  mortar  used  to  turn  the  brick  arches  in  which  the  beams 
were  embedded.  Corrosion  was  well  established  in  every  inch  of 
their  surface.  Had  any  moisture,  as  in  the  case  of  the  Times  build- 
ing, reached  them,  their  condition  would  have  been  fully  as  bad. 

The  iron  beams  supporting  the  sidewalks  laid  about  forty  years 
ago  in  •  New  York  City,  that  were  removed  for  the  Rapid  Transit 
Tunnel  work,  invariably  show  deep  corrosion  from  the  destruction 
of  the  paint  coatings  from  the  caustic  action  of  the  lime  mortar, 


*  A  full  list  of  the  series  of  electro-chemical  elements  having  a  metallic  base 
and  entering  into  the  composition  of  pigments  is  given  in  Chapter  XXXVI. 


CAUSTIC  ACTION  OF  MORTAR   UPON  PAINT. 


269 


also,  that  the  dried  mortar  is  not  a  protection  from  corrosion,  but  a 
promoter  of  it,  if  moisture  or  air  can  reach  the  surface  so  covered. 


FIG.  38. — Corrosion  of  sidewalk  iron  beams. 


Hydraulic,  also  quicklime  mortar,  only  prevent  corrosion  so  far 
as  they  are  free  from  mill-scale  and  continuously  dry  to  exclude 
the  air.  The  paint  coating  when  burned  by  the  caustic  action  of 
mortar  or  cement,  adds  no  material  period  to  the  life  of  the  iron 
and  except  for  appearance  and  protection  during  construction,  might 
be  left  off.  (See  Chapter  XV.) 

The  modern  hollow  tiles  used  for  floor  arches  and  building  partitions 
with  their  advantages  over  brickwork,  do  not  remove  the  cause  of 
the  corrosion  of  any  iron  that  they  may  be  in  contact  with. 

Gypsum,  while  not  caustic,  is  hydrometic,  and  the  continual  pres- 
ence of  moisture  is  fatal  to  ferric  bodies;  besides,  it  is  not  always 
free  from  caustic  substances  developed  in  the  calcination  of  it. 

The  following  cement  for  the  levelling,  bedding,  and  in  contact 
with  metal  work,  is  recommended.  The  cement  hardens  like  stone, 
is  impervious  to  water,  and  can  be  applied  by  a  trowel  from  a  mortar- 
board, over  walls  or  to  lay  brick  wherever  mortar  can  be  used.  It 
is  made  from  marble  dust  (from  marble  sawing  or  pulverizing  mills) 
mixed,  viz.: 

Pulverized  marble 62  per  cent. 

Sharp  silicious  clean  sand 35   ' '      ' ' 

Litharge 3   "      " 


270  CAUSTIC  ACTION  OF  MORTAR   UPON  PAINT. 

These  proportions  can  be  varied  somewhat  without  injury.  Too 
much  limestone  impairs  the  hardness;  too  much  sand  makes  the 
cement  porous.  When  the  mastic  is  to  be  used,  for  every  100  parts 
of  such  mixture,  7  parts  of  linseed-oil  are  required  to  bring  it  to  a 
good  trowel  paste.  The  oil  can  be  either  raw  or  boiled,  according 
to  the  time  of  drying  required.  The  surfaces  to  which  it  is  to  be  applied 
should  be  dry,  clean,  and  preferably  coated  with  linseed-oil  or  a  good 
carbon  paint,  before  the  application  of  the  cement. 

A  refined  bitumen  coating  applied  to  the  bright  metal,  hot,  has 
proven  to  be  the  best  of  coatings  for  ironwork  laid  in  cement,  mortar, 
or  concrete,  to  correct  the  caustic  action  of  them. 

The  metal  work  of  the  movable  dam  at  Lake  Wennibioskish, 
Minn.,  constructed  in  1899-1900,  was  cleaned  bright  by  the  sand- 
blast and  then  painted  three  coats  of  Edward  Smith's  Co.'s  Durable 
Paint,  applied  one  week  apart,  each  coating  being  thoroughly  dry 
before  the  application  of  the  next.  Observation  of  the  paint  in 
1901  showed  that  the  coatings  had  been  completely  killed  and  ab- 
sorbed wherever  the  painted  metal  was  embedded  in  the  concrete. 
The  metal  was  as  clean  as  before  painting,  with  a  slight  discoloration 
of  the  surface  of  the  concrete  from  the  paint  absorbed.  The  metal 
exposed,  however,  did  not  show  the  same  tendency  to  rust  quickly, 
as  before  the  application  of  the  paint,  on  the  short  exposure  before 
again  being  put  in  place.  The  surfaces  not  in  contact  with  concrete 
were  in  good  condition. 


CHAPTER  XXVIII. 

SAND-BLAST  AND   PICKLING   PROCESSES. 

THE  sand-blast  is  the  most  satisfactory  and  simplest  method  of 
cleaning  all  surfaces  for  painting,  whether  at  the  shops  or  in  situ. 


FIG.  39. — Sand-blast  apparatus. 

The  invention  of  the  sand-blast  is  due  to  General  Benj.  Tilghman, 
and  was  patented  October  18,  1870,  No.  108,408,  but  has  since 
expired.  There  are  some  patents  for  sand-blast  apparatus  of  subse- 
quent date,  issued  to  other  parties  for  improvements  relative  to 
portability,  clogging  of  the  sand  in  the  case,  etc.,  still  in  effect. 

Fig.  40  shows  a  portable  sand-blast  apparatus  used  by  Mr.  Geo. 
W.  Lilly,  C.E.,  for  cleaning  railway  viaducts  in  the  city  of  Colum- 
bus, Ohio. 

The  principal  features  of  the  sand-blast  consist  in  the  use  of 
compressed  air  at  a  pressure  of  from  15  to  25  pounds  per  square 
inch,  discharged  through  one  or  more  chilled-iron  or  hardened-steel 
nozzles  T%  inch  in  diameter,  which  are  directed  upon  the  work  to  be 
cleaned.  By  suitable  devices,  into  this  current  of  air,  dry  sharp  sand 

271 


272 


SAND-BLAST  PROCESS. 


or  coarsely  powdered  quartz  is  fed  at  the  rate  of  about  10  cubic  feet 
per  hour  for  each  nozzle,  which  discharges  about  120  cubic  feet  of 
free  air  per  hour,  or  about  1  cubic  foot  of  sand  to  1000  cubic  feet 
of  free  ah-  per  hour.  The  nozzles  wear  rapidly  and  require  frequent 


FIG.  40. — Portable  sand-blast  machine. 

renewal,  but  they  are  of  small  or  minor  expense.  The  2  or  2J-inch 
diameter  armor-clad  rubber  hose  that  conducts  the  compressed  air 
from  the  air-receiver  to  the  place  of  work  being  soft  and  elastic,  is 
comparatively  little  affected  by  the  current  of  sand  and  air,  unless 
the  air  is  hot;  hence  methods  to  cool  the  air  before  it  reaches  the 
leading  hose 'are  necessary.  Four  such  nozzles  that  gradually  wear 
to  }-inch  diameter  and  then  discharge  200  to  240  cubic  feet  of  air 
per  hour,  require  an  air-compressor  of  20  inches  diameter  for  steam 
and  22-inch  air-cylinders,  by  24-inch  stroke  or  approximate  sizes, 
also  a  150  H.P.  boiler. 


SAND-BLAST  PROCESS.  273 

The  abrading  material,  when  used,  must  be  thoroughly  dry,  and 
can  be  used  four  or  five  times  over,  or  until  it  is  broken  into  a  powder 
too  fine,  or  becomes  too  dirty  to  be  effective. 

For  cleaning  ships'  bottoms  in  dry  dock,  where  the  rust  and 
paint  coatings  are  generally  thick  and  somewhat  softened  by  the 
water,  about  -&  square  foot  of  metal  is  cleaned  per  minute,  or  48 
to  60  square  feet  per  hour.  This  costs  about  3  cents  per  square 
foot  of  surface,  as  the  waste  of  sand  is  greater  and  the  work  cannot 
be  done  so  advantageously  in  a  dry  dock  as  in  a  shop. 

On  the  New  York  Elevated  Railway  Station  at  155th  Street  an 
average  of  80  square  feet  per  hour  was  maintained  for  a  number  of 
months  in  removing  a  hard  coating  of  old  paint  and  rust  to  the  bright 
iron.  The  loss  of  time  in  changing  nozzles  and  shifting  scaffolds 
was  about  one  hour  per  day  per  nozzle.  The  labor  account  was 
one  man  to  hold  and  direct  each  nozzle;  one  man  to  attend  to  two 
sand-boxes,  and  one  man  to  clean  up  and  supply  sand  for  the  four 
nozzles  or  seven  men  per  corps  the  men  shifting  their  scaffolds  with- 
out other  aid.  The  four-nozzle  plant  for  bridge  or  viaduct  clean- 
ing will  clean  about  2500  square  feet  of  surface  per  eight-hour  day 
at  an  expense  of  about  $20  for  all  iterrs,  except  the  man  and  coal  for 
the  compressor,  or  8  cents  per  square  foot,  which  would  be  modified 
by  the  amount  of  cleaning  for  each  structure. 

Removal  at  the  shop  of  mill-scale  and  dirt  is  done  at  the  rate 
of  4^  to  5  square  feet  of  surface  per  minute,  or  270  to  300  square  feet 
per  hour  per  nozzle,  or  about  J  cent  per  square  foot  of  surface.  With 
an  organized  corps  and  plant,  the  cost  of  cleaning  surfaces  need  not 
exceed  J-  cent  per  square  foot  of  surface,  large  or  small,  or  about  one- 
third  the  labor-cost  of  the  painter  on  a  first-class  coat  of  paint,  and 
requires  about  the  same  degree  of  skilled  labor  as  painting. 

The  metal-work  of  the  movable  dam  at  Lake  Wennibioskish, 
Minn.,  erected  during  1900,  was  cleaned  bright  by  an  extemporized 
sand-blast.  A  hoisting-engine  run  backward  furnished  the  com- 
pressed air,  an  old  steam-boiler  was  used  for  an  air-receiver,  gas- 
pipe  for  nozzles,  and  garden  hose  for  leaders,  etc. 

Mr.W.  C.Weeks,  C.E.,*  reports  "that  four  laborers  and  one  engineer 
in  charge  of  the  apparatus  cost  for  labor  $9.22  and  $2.50  for  fuel.  On 
general  surfaces,  40  square  feet  per  hour  were  cleaned,  using  two  nozzles, 

*  Engineering  Record,  May  4,  1901. 


274  SAND-BLAST  PROCESS. 

or  a  cost  of  $0.036  per  square  foot.  On  plates  and  large  straight  sur- 
faces, 90  square  feet  per  hour  was  the  usual  rate  of  cleaning,  which 
cost  $0.016  per  square  foot." 

In  a  number  of  United  States  navy-yards,  with  well-equipped, 
permanent,  and  fairly  perfect  sand-blast  plants,  the  cost  of  cleaning 
averages  £  cent  per  square  foot  of  surface.  This  for  plates  ^-inch 
thick  is  98  cents;  for  i-inch  plates,  $1.95  to  $2.00  per  ton.  To 
sand-blast  7-inch  I-beams  weighing  17.5  pounds  per  foot  costs 
$1.35  per  ton;  12-inch  I-beams,  weight  50  pounds  per  foot,  cost  80 
cents  per  ton. 

The  average  cost  for  cleaning  plate-girder  bridges  in  situ  is  proba-* 
bly  $1.00  per  ton  of  metal.  For  truss  and  lattice-iron  bridges  the 
cost  of  sand-blasting  ranges  from  $1.00  to  $1.75  per  ton. 

The  United  States  Army  Engineer  Corps  cleaned  50,000  square 
feet  of  steel  lock-gates  and  other  metal  on  the  Muscle  Shoals  Canal 
during  1898-99  from  a  temporary  floating  plant.  The  cost  of  all 
items,  was  3  cents  per  square  foot,  and  the  new  coat  of  paint  cost 
2.88  cents  per  square  foot. 

Mr.  Geo.  W.  Lilly,  C.E.,  reports  the  cleaning  by  sand-blast  of  a 
number  of  railway  bridges  and  viaducts  in  the  city  of  Columbus, 
Ohio.  The  work  was  done  under  exceptionally  adverse  circum- 
stances, but  indicated  that  8  cents  per  square  foot  covered  all  the 
expenses.  For  cleaning  a  viaduct  over  the  Little  Miami  Railway, 
containing  25,000  square  feet  of  surface  in  a  confined  location  where 
the  cleaning  was  interrupted  by  the  train-service  that  frequently 
amounted  to  one-fifth  of  the  working  hours,  the  cost  of  the  work, 
including  flagman,  sand  and  drying,  compressed  air,  and  all  other 
expenses,  including  the  labor,  was  3.04  cents  per  square  foot.  On 
the  best  days,  in  a  favorable  location  uninterrupted  by  the  trains, 
1227  square  feet  were  cleaned  per  day  at  a  cost  of  1.23  cents  per 
square  foot.  On  a  plate  girder  containing  3727  square  feet,  the 
cost  was  2.37  cents  per  square  foot. 

The  pressure  of  air  ranged  from  25  to  38  pounds,  averaging  33 
pounds  per  square  inch.  The  nozzles  wore  rapidly.  They  were 
of  i-inch  extra  heavy  wrought-iron  gas-pipe,  about  2  feet  long  and 
lasted  from  3  to  5  hours  each. 

The  expense  of  handling  structural  metal  at  the  shops  after  machin- 
ing preparatory  to  sand-blasting  it,  ranges  from  40  cents  to  $1.50 
per  ton  according  to  the  weight  and  character  of  the  pieces  and  facili- 
ties of  the  plant. 


CLEANING  PROCESS.  275 

A  recognition  of  the  fact  that  structural  steel  is  a  perishable 
material,  requiring  thorough  protection  from  corrosion  during  all 
the  stages  of  its  manufacture  and  use,  should  be  required  of  every 
engineer,  and  the  subject  should  form  an  important  part  of  his  edu- 
cation. There  is  no  part  of  structural  engineering  needing  a  more 
thorough  reform  in  both  spirit  and  practice  than  this  one. 

The  apparent  indifference  regarding  the  future  fate  of  steel  mate- 
rial, after  it  is  in  location,  is  probably  due  to  the  mistaken  economy 
of  the  engineer  corps  and  the  proprietors,  on  account  of  the  added 
cost  of  properly  cleaning  the  metal.  If  cleaning  is  necessary,  as  engi- 
neers and  all  admit,  it  should  be  specified  in  the  contract,  properly  done, 
inspected  by  a  competent  person,  and  paid  for  like  any  of  the  other 
processes,  and  the  penalty  for  its  non-fulfilment  be  as  strictly  enforced 
as  for  a  badly  driven  rivet  or  poorly  machined  or  fitting  part.  The 
above  deficiencies  are  readily  detected  and  can  be  corrected,  but  the 
poorly  cleaned  surface  escapes  notice  and  is  readily  put  out  of  evi- 
dence by  the  handy  paint-pot. 

It  is  the  imperative  duty  of  the  engineer  in  charge  of  structural 
work  to  require  his  inspector  to  perform  his  duty  at  all  times  so  that 
a  radical  change  shall  be  had  from  the  present  practice  of  cleaning 
and  painting  ferric  metal,  the  corrosion  of  which  is  now  too  much  in 
evidence. 

At  a  late  meeting  of  an  engineering  society,  the  protection  of 
ferric  structures  from  corrosion  was  under  consideration  by  oral 
discussion  and  correspondence.  The  cleaning  of  the  surface  of  steel 
to  the  absolutely  clean  metal  by  some  method,  preliminary  to  the 
immediate  painting  of  it  under  cover,  was  unqualifiedly  endorsed. 
And  yet  within  the  limits  of  a  ten-mile  circle  from  the  engineers' 
meeting  there  were  many  thousands  of  tons  of  ferric  structural  mate- 
rial in  process  of  erection  by  the  engineers  represented  at  the  meeting, 
and  scarcely  a  ton  of  this  material  had  received  any  other  cleaning 
than  that  from  a  putty  knife  or  a  whisk-broom.  The  quality  of  the 
applied  paint  in  many  cases  was  as  deficient  as  the  cleaning.  So 
much  for  theory  versus  practice. 

Pickling  the  metal  instead  of  sand-blasting  it  is  more  practised 
by  European  than  American  engineers,  especially  for  structural  work. 
Mill-scale  is  readily  removed  by  immersing  the  metal  in  a  hot  dilute 
solution  of  sulphuric  acid.  Generally,  6  to  12  minutes  suffices,  using 
a  25  to  28  per  cent  acid  solution.  A  10  or  12  per  cent  solution  is 
effective,  but  requires  more  time  in  the  bath.  The  stronger  solutions 


276  PICKLING  PROCESS. 

are  recommended.  They  are  equally  as  safe  to  handle  and  should 
be  applied  hot  if  possible;  the  latter  quality  is  best  for  removing  the 
scale. 

In  foreign  navy-yards,  9  to  10  per  cent  hot  solutions  are  used, 
the  metal  remaining  in  the  bath  five  or  more  hours,  according  to  the 
quality  of  the  scale.  This  requires  a  large  pickling  plant  and  has  no 
other  advantages.  When  appearance  or  test  shows  the  scale  is  loos- 
ened, the  metal  is  removed  and  well  washed  by  a  copious  and  strong 
jet  of  water  under  75  pounds  or  more  pressure. 

Soaking  the  metal  in  baths  of  still  or  light  running  water  does 
not  thoroughly  remove  the  acid.  The  still- water  bath  is  the  cause 
of  the  failure  of  tin-plate. 

Pickled  metal  is  liable  to  become  coated  with  a  tough,  gummy 
substance,  quite  difficult  to  remove,  except  by  the  friction  from  a 
strong  jet  of  water.  Arsenic  in  the  sulphuric  acid  made  from  pyrites 
also  adds  to  the  gummy  deposit  precipitated  on  the  metal.  Acid 
free  from  arsenic  should  be  specified  for  the  pickle.  The  gummy 
deposit  prevents  the  paint  from  bonding  to  the  metal,  rendering  it 
liable  to  peel. 

After  the  metal  has  been  washed  by  the  jet  of  hot  or  cold  water 
it  should  be  immersed  in  a  bath  of  hot  lime-water  and  be  left  in  it 
long  enough  to  reach  the  temperature  of  the  bath,  in  order  to  neu- 
tralize any  of  the  acid  not  removed  by  the  water  jet.  It  is  then 
removed  and  dried,  preferably  in  an  oven.  The  coating  of  lime  left 
upon  the  metal  can  be  easily  brushed  off,  leaving  the  metal  clean  and 
bright,  which  will  show  evidences  of  rust  in  an  hour  if  not  painted 
immediately. 

Muriatic  acid  is  sometimes  used  in  place  of  sulphuric  acid  for  the 
pickle.  It  is  not  as  effective  as  sulphuric  acid,  it  costs  more,  and  the 
gummy  coating  formed  by  the  pickle  is  more  difficult  to  remove, 
requiring  a  hot  alkaline  or  caustic-soda  bath,  instead  of  lime,  to  remove 
it.  A  solution  of  sulphate  of  zinc  is  effective  for  the  removal  of  this 
gummy  coating. 

Obviously  a  pickling  plant  requires  a  larger  space  for  an  equal 
cleaning  capacity  than  a  sand-blast,  and  is  not  so  convenient  to  use 
at  all  seasons  of  the  year,  and  both  are  impractical  to  use  in  the  con- 
struction tool  shops. 

The  labor  and  material  accounts  for  a  pickling  bath  for  all  sizes 
and  weights  of  ordinary  structural  steel  is  about  25  cents  per  ton. 
The  labor  account  for  moving  the  pieces  into  and  out  of  the  pickle, 


GASOLINE  PROCESS  FOR  CLEANING  METAL.  277 

cleaning  baths,  and  ovens,  will  be  from  50  cents  to  $2.00  per  ton, 
or  rather  more  than  is  required  for  a  sand-blast,  as  the  several  pieces, 
though  of  the  same  weight  and  character,  ha  veto  be  moved  more 
frequently. 

Steels  high  in  carbon,  or  cast-iron  articles,  are  difficult  to  pickle, 
as  a  film  of  graphitic  carbon  forms  on  the  surface  of  the  metal,  which 
mixes  with  the  gummy  deposit  from  the  acid  bath,  and  requires 
considerable  labor  and  care  to  remove. 

When  the  sand-blast  or  pickling  process  is  not  available,  mill- 
scale,  rust,  and  old  paint  coatings  are  removed  from  works  in  situ, 
by  the  gasoline  burning  torch,  followed  closely  by  the  scraper  and  wire 
brush. 

The  cost  of  the  burning  process  is  so  closely  connected  with  the 
painter's  labor  as  to  be  difficult  of  separation,  but  a  quart-burning 
torch  will  burn  3J  hours,  and  one  man  can  saturate  rust-spots  and 
burn  off  from  80  to  100  square  feet  of  surface  per  hour,  at  a  cost  of 
TO  to  T7¥  cent  per  square  foot  of  surface,  leaving  it  ready  for  the  painter. 

A  modern  parlor,  or  sleeping-car,  65  to  70  feet  long,  requires  three 
gallons  of  gasoline  to  burn  off  the  outside  paint  coating,  and  about 
four  days  of  time,  for  one  man  to  use  the  torch,  followed  by  two  men 
two  days  each,  to  sandpaper  ready  for  the  painter,  or  a  total  cost  of 
45  cents  for  the  gasoline,  and  $15.00  for  the  labor,  or  -^  to  1  cent 
per  square  foot  of  surface. 

Care  is  required  in  the  use  of  gasoline,  either  for  the  torch,  or  for 
saturating  the  old  paint,  as  explosions  and  serious  burning  of  the 
workmen,  and  fires,  are  frequent.  Insurance  companies  forbid  the 
use  of  either  the  torch  or  fluid  for  the  removal  of  paint  or  rust  in  any 
building  covered  by  their  policies. 

Any  material  that  can  be  inclosed  in  a  chamber  or  iron  casing 
and  subjected  to  the  action  of  a  bath  of  low-pressure  steam  for  20 
to  25  minutes  will  have  the  old  coatings  softened,  when  they  can  be 
easily  scraped  off.  This  is  to  be  followed  by  a  thorough  washing 
with  soap  and  water,  and  rinsing.  A  pair  of  locomotive  driving- 
wheels  required  30  minutes  to  scrape  and  wash  after  steaming.  The 
total  cost  being  about  one-third  to  one-half  that  required  for  the 
usual  caustic-soda  application. 

Many  railway  repair  shops  use  the  following  mixture  for  the 
removal  of  old  paint.  It  has  no  action  upon  rust.  Caustic  soda 
and  sal-soda,  each  30  pounds;  mix  with  3  pounds  of  strong  ammonia 
diluted  with  30  gallons  of  water.  To  the  above,  add  a  mixture  of 


278  OTHER  PROCESSES  FOR  CLEANING  METAL. 

30  pounds  of  finely  ground  quicklime  in  5  gallons  of  water,  and  3  to  4 
pounds  of  melted  laundry  or  soft  soap.  The  two  mixtures  added 
together,  when  cold,  should  be  of  the  consistency  of  putty.  It  is 
applied  by  a  trowel  or  stiff  4-inch  flat  brush  in  successive  coats  about 
•J  to  J  inch  thick.  Care  must  be  used  in  mixing  the  lime.  A  stirring- 
paddle  should  be  left  in  the  tub  to  form  a  vent  to  prevent  the  caustic 
mixture  from  blowing  out. 

The  cost  to  remove  the  paint  from  a  pair  of  locomotive  driving- 
wheels  by  this  mixture  is  65  cents  for  material  and  15  hours  of  labor 
at  $2.25,  or  a  total  of  $2.90.  Careful  washing  with  hot  water  to  remove 
all  traces  of  the  caustic-soda  paste  is  required,  as  for  all  strong  alka- 
line mixtures. 

Wooden  surfaces  treated  with  caustic-soda  compounds  to  remove 
paint  or  varnish  are  injured  by  the  raising  of  the  grain  of  the  wood, 
which  cannot  be  restored  by  sand-papering.  The  parts  so  treated 
show  spotted;  even  a  staining-coat  will  not  cover  them  uniformly. 
Fine  woods  are  injured  the  worst. 


CHAPTER  XXIX. 

FERRIC-PAINT   TESTS. 

OBJECTION  is  made  by  some  engineers  and  paint  manufacturers 
to  the  immersion  methods  of  testing  paints;  that  they  do  not  meet 
the  actual  conditions  of  coatings  exposed  to  weather;  that  a  ferric 
structure  is  not  always  wet,  but  wet  and  dry,  with  more  dry  hours 
than  wet,  etc.  This  would  depend  altogether  upon  the  location  of 
the  structure;  in  many  instances  there  might  be  more  wet  or  damp 
hours  than  dry  ones.  A  fog  or  long-continued  sweat  is  more  destruc- 
tive to  a  paint  coating  than  a  passing  storm.  But  the  plain  fact 
remains  that  these  tests  are  all  competitive  as  between  different 
commercial  paints,  and  under  uniform  conditions.  The  trial  given 
one  paint  is  given  to  all;  the  few  successful  ones  are  the  better  ones 
to  select  from  to  base  any  subsequent  improvements  or  experiments 
upon,  or  for  use.  The  water-test  settles  the  merit  of  a  protective  coat- 
ing in  short  order,  and  so  soon  as  generally  adopted  by  those  ordering 
paints  for  the  protection  of  ferric  structures  exposed  to  weather,  so 
soon  will  the  great  majority  of  these  patent  paint  compounds  cease 
to  vex  the  engineer  with  high  claims  and  low  performance. 

The  nearer  any  protective  coating  approximates  an  enamel  or  var- 
nish, generally  the  more  durable  it  will  be.  The  Japanese  and  Chinese 
lacquers  are  varnishes,  and  dry  better  by  the  application  of  water 
than  in  dry  air  alone,  and  all  compounded  varnishes  are  hardened  in 
the  last  stages  of  their  drying  by  water.  Lacquers  when  thoroughly 
dry  remain  unchanged  for  scores  of  years,  when  exposed  to  fresh  or 
salt  water  either  hot  or  cold  or  alternately  wet  and  dry,  or  immersed 
for  years.  The  coming  ferric  protective  coating  will  probably  be  a  true 
varnish  with  a  carbon  or  graphite  pigment.  But  it  will  be  well  to 
bear  in  mind  that  it  will  not  be  imperishable  in  exposed  locations, 
and  that  its  application  and  the  preparation  of  the  structure  to  receive 
it  will  require  more  attention  than  at  the  present  time  these  matters 
receive;  neither  will  it  be  a  low-cost  article. 

279 


280  FERRIC-PAINT  TESTS.     SMITH'S  TESTS. 

Tests  of  Twenty-seven  English  Commercial  Ferric  Paints. 

In  a  paper  *  read  before  the  Newcastle,  England,  section  of  the 
Society  of  Chemical  Industry,  Mr.  Henry  Smith,  F.I.C.,  described 
a  series  of  experiments  upon  the  protective  powers  of  twenty-seven 
different  English  commercial  paints,  as  applied  to  ironwork  in  fifty 
separate  instances.  The  methods  of  test  were  those  devised  and 
employed  by  Mr.  Max  Toltz,  C.E.,  in  a  series  of  experiments  upon  a 
number  of  American  commercial  protective  coatings  for  iron  in  1897. f 
Three  sets  of  bright  and  clean  iron  plates,  all  of  the  same  size,  were 
respectively  coated  with  the  several  paints,  in  all  cases  furnished  as  a 
stiff  paste,  and  when  applied,  were  brought  to  the  consistency  of  a 
paint  by  mixing  with  genuine  boiled  linseed-oil,  capable  of  drying 
in  seven  hours  under  ordinary  conditions  of  temperature,  no  driers 
being  used.  The  first  coat  was  allowed  to  dry  thoroughly  firm  before 
the  second  coating  was  applied.  When  this  also  was  firm  and  hard, 
one  set  of  the  plates  was  exposed  to  the  weather,  as  in  ordinary  cases 
of  painted  structures.  The  other  two  sets  were  treated  as  follows: 
One  set  was  simply  to  corroborate  the  results  obtained  from  the 
other  set,  the  results  being  practically  identical  in  each  case.  Each 
painted  strip  was  placed  in  a  clean,  wide-mouthed  glass  bottle,  half 
filled  with  clean  pure  water.  The  bottles  were  not  closed,  but  were 
protected  from  the  entrance  of  dust  and  impurities  while  allowing  the 
air  free  access  to  the  painted  plates.  Several  of  the  plates  had  com- 
menced to  corrode  in  about  a  week.  This  was  indicated  by  a  cloudi- 
ness in  the  water,  which  afterward  became  further  oxidized,  and 
formed  a  red  precipitate  of  ferric  oxide,  which  subsided  partly  to  the 
bottom  of  the  vessel.  After  three  months'  exposure  the  plates  were 
removed,  and  the  liquid  in  each  bottle,  together  with  the  sediment, 
was  tested  for  the  percentage  of  iron  present  in  the  form  of  rust. 

The  figure  given  as  denoting  the  amount  of  corrosion  is  less  than 
the  actual  amount,  as  it  does  not  include  the  portion  that  adhered 
to  the  plate,  and  was  not  scraped  or  brushed  off,  and  would  not  drain 
off.  In  each  case  the  weight  of  rust  was  calculated  to  pounds  of  rust 
per  1500  square  yards  of  painted  surface;  the  other  figures  give  the 
percentage  composition  of  the  several  paints  by  weight. 

*  Engineer   (London)   and  the   American  Gas  Light  Journal  (New  York), 
•j"  September  4-20,  1899.     Journal  of  the  Association  of  Engineering  Societies, 
St.  Paul,  Minn.,  1897. 


FERRIC-PAINT   TESTS.     SMITH'S  TESTS. 


281 


CONDITION    AFTER    THREE   MONTHS'    EXPOSURE. 

Pounds  of  Rust  from  1500  Square  Yards  of  Surface. 

Corrosion. 

6  samples  of  red  lead  alone,  or  mixed  with  barytes  50% ;   raw   oil,  10.00%  None. 
Red  lead.  .  .22.00% ;  barytes,    66.00% ;  total,  88.00% ;      "      "    12.00%      " 
"       "...33.33%;        "          58.SO%;     "..92.13%;      "      "      7.87%      " 

3  samples  zinc  oxide,       "  45.00%; "      "    10.00%  Trace. 

Zinc  oxide.  .27.27%;        "          63.63%;    "    ..90.90%;  boiled  oil,  9.10%      " 

White  lead,  pure 92.56%; "      "      7.44%    751bs. 

White  lead.  .53.78;      barytes    40.33%;     "     ..94.11%;     "      "      5.89%    80   " 

"        "       50.52%;        "          42.10%;     "     ..92.62%;     "      "      7.38%    95    " 

Iron  oxide,  pale  (50%  Fe2O3).  -83.60%; 

"     deep  (96%  Fe2O3).  -86.89%; raw  oil,  13.11%  123 

"     Venetian  red 7.55%  ) 

Barytes 80.57%  > 

Iron  oxide,  medium  color  (94% 

Fe203) 86.89%;  . 

Iron  oxide,   extra  bright  color 


..88.12%; 


16.40%    81   " 
13.11%  123  " 

11.88%  123  " 
13.11%  134  " 


(90%Fe203) 82.35%; 

Iron  oxide,  pure  (90%  Fe2O3)  .  76.30% ; 

"          "     medium 12.30% 

Barytes 76.22% 

Indian  red  (70%  Fe-A) 82.35%; 

Turkey  red  (95%  Fe2O3) 81.16%; 

Iron  oxide 27.03%  ) 

Barytes  and  calcium  carbonate. 62. 52%  ) 
Barytes    (natural    barium    sul- 
phate)  88.00%;  , 

Iron  oxide,  Venetian  red 8.47%  } 

Barytes  and  calcium  carbonate. 78.80%  ) 


..88.52%; 


..89.55%; 


..87.27%; 
..86.07%; 
..92.39%; 


17.65%  137  " 

23.70%  160  " 

11.48%  244  " 

17.65%  227  " 

18.84%  262  " 


12.00%  155  " 
12.73%  118  " 


12.14%  242  " 
7.61%  266  " 


Iron  oxide 13.93%  > 

Barytes  and  calcium  carbonate. 60.00%  J- 
Rose  pink  (principally  barytes)  .12.14%  ) 
Barytes  and  calcium  carbonate.80.56%  "I 

Celestial  blue 11.83%  / 

Barytes  and  calcium  carbonate. 68. 99%  ^ 

Ivory  and  carbon  black 8.42%  v 

Manganese  dioxide 2.46%  J 

Barytes  and  calcium  carbonate. 79. 30%  \ 

Carbon  and  bone  black 4.35%  I 

Manganese  dioxide 1.30%  J 

Drop  black  (charcoal  black)  . .  .  60.00% ;  . 

Flake  graphite,  pure 69.56% ; raw  oil,  30.44%  215  " 

Boiled  linseed  oil,  pure 500  " 

Raw  Turkey  umber 51.85%; raw  oil,  48.15%  510  " 


. .  79.87% ;  boiled  oil,  20.13%  352  " 

..84.95%;   raw  oil,  15.05%  392  " 
boiled  oil,  40.00%  250  " 


282  FERRIC-PAINT   TESTS.     SMITH'S   TESTS. 

Twenty  mixtures  of  barytes  alone,  or  with  calcium  carbonate 
mixed  with  celestial  blue,  Prussian  blue,  chrome-yellow,  raw  sienna, 
Vandyke  brown,  Italian  ochre,  Brunswick  and  other  greens,  chromate 
of  lead,  English  umber,  Turkey  umber,  ultramarine,  Chinese  blue, 
burnt  sienna,  mixed  with  raw  oil  in  proportions  from  11  per  cent  to 
51  per  cent  of  the  weight  of  the  paint;  the  corrosion  in  the  order 
named  above  ran  from  168  pounds  to  441  pounds  per  1500  square 
yards  of  surface. 

Except  in  the  case  of  the  blues,  umbers,  siennas,  etc.,  where  the 
pigment  had  but  little  influence  on  the  oil  to  resist  decay  beyond 
that  inherent  in  the  oil  alone,  the  more  separate  substances  that 
entered  into  the  composition  of  the  pigment,  the  more  unreliable  it 
became.  A  single  exception  is  noted  in  the  case  of  a  Venetian  red 
paint,  made  from  barytes,  calcium  carbonate,  and  a  small  amount  of 
iron  oxide,  that  gave  a  better  result  than  barytes  alone,  or  when 
barytes  was  mixed  with  the  other  color  pigments  of  much  less  specific 
gravity.  Several  substances  in  a  composite  paint  are  generally  fatal 
to  its  protective  qualities,  no  matter  to  what  it  is  applied.  The 
several  atoms  of  these  substances,  even  if  uniformly  distributed  in  the 
pigment  in  the  process  of  grinding,  bolting,  and  mixing  (but  they  are 
not),  will  not  retain  their  juxtaposition  when  mixed  with  the  oil. 
The  heavy  atoms  will  sink,  and  there  will  be  a  marked  difference  hi 
the  coating  spread  from  the  top  of  the  paint  in  the  pot  from  that  in 
the  middle  or  bottom;  the  lightest  and  most  perishable  substances 
will  get  on  the  surface  firs 

Barytes  worked  well  with  red  lead  and  zinc  oxide,  there  being  but 
a  small  difference  in  their  specific  gravities  as  compared  with  barytes 
and  the  other  color  or  base  pigments.  With  white  lead,  as  the  per- 
centage of  barytes  was  increased,  so  was  the  corrosion.  Aside  from 
the  reduction  in  cost  of  these  lead  and  zinc  pigments  by  the  addition  of 
barytes,  there  is  no  reason  for  its  use,  as  the  barytes  alone  did  not 
give  a  satisfactory  test.  No  doubt  from  the  splintery  character  of 
its  atoms,  as  has  been  before  commented  upon,  it  is  wholly  destitute 
of  covering  or  coloring  power.  The  vagaries  of  the  iron-oxide  paints 
in  the  varying  proportions  of  the  pigment  and  oil  are  noticeable,  but 
not  so  marked  as  where  barytes,  one  of  the  heaviest  of  all  pigments, 
and  calcium  carbonate,  one  of  the  lightest,  both  classed  as  inert 
pigments,  were  mixed  with  the  oxide,  and  fully  sustained  the  pre- 
vious remarks  upon  the  non-protective  character  of  composite  and 
iron-oxide  paints.  Boiled  oil,  in  the  single  instance  reported,  proved 


FERRIC-PAINT  TESTS.    SMITH'S  DISH-TESTS.  283 

superior  to  raw  oil  as  a  vehicle  for  the  several  iron-oxide  paints  in  the 
ratio  of  one  to  nearly  five. 

Smith's  Dish-tests  of  Paints. 

A  second  series  of  experiments  were  made  by  the  same  experi- 
menter, and  following  the  method  of  Mr.  Max  Toltz,  C.E.,  to  wit: 
A  number  of  iron  dishes  five  inches  in  diameter  and  one-half  inch  deep 
were  scoured  bright,  and  then  coated  with  two  coats  of  the  several 
paints  used  upon  the  above-detailed  iron  plates  and  under  the  same 
conditions  as  to  the  composition  and  drying  of  the  paints.  These 
shallow  dishes  were  filled  with  water  and  allowed  to  completely 
.evaporate  in  the  open  air  of  the  laboratory.  This  operation  was 
repeated  six  times  in  the  course  of  six  months.  Thus  tested,  the  only 
paints  which  remained  practically  unaffected  were  red-lead  and 
orange-lead  paints,  some  of  which,  however,  such  as  the  "vermilion- 
ette"  and  scarlet-red  paints,  contained  a1  so  a  proportion  of  aniline 
colors,  while  two  of  the  red-lead  paints  contained  in  the  one  case 
45  per  cent  of  barytes  and  in  the  other  66  per  cent.  All  the  other 
dishes  were  more  or  less  rusted,  the  order  of  merit  of  the  better  paints 
being  as  follows: 

1st.  Zinc  oxide. 

2d.  Equal  parts  zinc  white  and  barytes. 

3d.  Zinc  white,  3  parts;  barytes,  7  parts. 

4th.  Lithopone  (a  mixture  of  zinc  sulphate,  zinc  oxide,  and  barytes). 

5th.  Pure  white  lead. 

6th.  White  lead,  5.37  parts;  barytes,  4.03  parts. 

7th.  White  lead,  5.05  parts;  barytes,  4.21  parts. 

All  the  other  paints,  thirty-six  in  number,  proved  inefficient. 
The  first  to  show  rust  was  that  one  painted  simply  with  linseed-oil. 
The  above  classification  of  merit  is  by  Mr.  Smith,  and,  taken  together 
with  the  detailed  report  of  the  glass-bottle  test  (before  given),  may 
be  considered  a  fair  representation  of  the  protective  qualities  of  the 
hundreds  of  commercial  ferric  paints  foisted  upon  the  market  under 
various  trade-mark  names  in  the  United  States  as  well  as  in  England, 
where  the  above  experiments  were  conducted. 

Both  the  immersion-  and  dish -tests  are  very  important  for  deter- 
mining in  a  relatively  short  time  the  weather-resisting  power  of  a 
paint.  If  the  coating  is  unable  to  resist  the  action  of  water  or  moisture 
in  the  form  of  steam,  fog,  or  vapor  from  a  tunnel  or  other  confined 
space,  it  cannot  be  desirable  for  the  protection  of  a  ferric  structure, 


284  FERRIC-PAINT  TESTS.     TOLTZ'S  DISH-TESTS. 

or  even  a  wooden  one.  The  dish-test,  probably,  is  the  nearest  to  the 
actual  condition  which  a  paint  must  withstand.  When  the  water 
in  the  dish  is  nearly  evaporated,  there  remains  in  the  circular  seam 
of  the  bottom  a  film  of  water  which  contains  the  carbonic  acid  and 
the  decomposing  gases  and  dirt  from  the  atmosphere,  which  act 
upon  the  paint  in  such  a  way  that  the  coating  at  that  part  is  soon 
permeated  and  rust  forms.  This  action  is  more  and  more  developed 
after  each  evaporation,  and  practically  covers  the  whole  dish  in  a 
short  time.  In  actual  service  the  same  thing  will  happen.  The 
corner  of  the  dish  finds  its  counterpart  in  every  corner  of  a  ferric 
structure  where  two  plates,  angles,  or  other  parts  join.  Rust  will 
commence  at  those  seams  and  extend  under  the  paint,  but  will  not 
show  as  plainly  on  a  bridge-truss  as  on  the  small  dish. 

Toltz's  Tests  of  American  Commercial  Ferric  Paints. 

The  shallow-dish  tests  by  Mr.  Max  Toltz,  C.E.  (before  referred  to), 
were  made  prior  and  during  1897,  and  extended  over  a  period  of 
from  six  months  to  two  years.  Without  entering  into  as  great  detail 
as  that  quoted  from  Professor  Smith,  the  deductions  from  his  tests 
are  in  brief.  Twenty-two  different  paints  were  submitted  to  test 
under  the  following  classification: 

No.  1.  True  asphaltic  varnish  paints  compounded  by  heat  in  the 
same  manner  as  a  black  baked  japan,  and  practically  of  the  same 
nature  and  comparable  therewith.  No  corrosion  reported  after  the 
dishes  had  been  filled  and  evaporated  naturally  fourteen  tunes. 

No.  2.  So-called  asphaltic  varnishes,  or  paints  of  inferior  qualities 
to  the  above  No.  1,  made  from  asphaltum  dissolved  in  benzine  or 
other  volatile  vehicle,  but  were  not  a  true  varnish.  They  contained 
about  43.5  per  cent  of  vehicle  and  56.5  per  cent  reported  to  be  as- 
phaltum. As  a  rule  they  showed  well  in  the  beginning,  but  after  the 
volatiles  had  evaporated,  especially  when  subjected  to  a  moderate 
heat-test,  the  coatings  became  quite  brittle,  were  easily  removed 
by  abrasion,  and  did  not  protect  the  surface  covered  with  them. 
Their  composition  varied  in  the  several  specimens  tested.  One  sample 
analyzed  had  no  asphaltum  in  it.  Under  test  the  dishes  painted  one 
coat  showed  considerable  rust  all  over  after  the  fifth  exposure.  Those 
painted  two  coats  after  the  seventh  exposure  showed  not  much  better. 
Generally,  their  reliability  as  protective  coverings  for  ferric  struc- 
tures is  the  least  satisfactory  of  all  paints. 

No.  3.  Black-carbon  paints,  in  which  the  vehicle  was  practically 


FERRIC-PAINT  TESTS.     TOLTZ'S  DISH-TESTS.  285 

a  varnish,  the  carbon-black  and  other  pigments  being  ground  in 
practically  a  linseed-oil  varnish,  and  are  comparable  with  No.  1,  to 
which  they  are  closely  related.  The  dish  painted  with  only  one 
coat  showed  a  little  deterioration  at  the  end  of  the  fourteenth  evapo- 
ration, while  the  dishes  painted  two  coats  were  uninjured,  the  coating 
being  as  elastic  and  tough  as  when  first  applied. 

No.  4.  Iron-oxide  paints  consisting  of  more  or  less  iron  oxide 
with  more  or  less  silicious  matter,  and  compounds  of  lime  and  mag- 
nesia. They  were  of  different  grades  and  qualities,  were  as  a  rule 
well  ground  and  spread  well.  Under  test  on  the  dishes  painted  with 
one  coat,  after  the  fifth  exposure  many  rust-spots  appeared.  Those 
painted  two  coats  were  refilled  six  times,  and  on  them  the  rust  was 
plainly  discernible  to  the  eye. 

No.  5.  Graphite  paints  and  silica-graphite  compounds.  These 
paints  were  received  from  the  several  manufacturers  in  the  form 
of  a  stiff  paste,  and  when  mixed,  ready  to  apply,  4^  parts  of  paste 
to  3J  parts,  by  weight,  of  boiled  linseed-oil  were  used.  The  dishes 
painted  with  one  coat  were  evaporated  ten  times.  After  the  fifth 
evaporation  a  few  specks  of  rust  were  noticeable,  and  the  number 
gradually  increased  after  each  successive  evaporation.  After  the 
tenth  exposure  some  slight  difference  between  them  was  noticeable, 
but  not  much.  The  dishes  painted  two  coats  were  exposed  thirteen 
times  in  two  years,  and  none  of  them  showed  any  rust  or  indication 
of  rust.  The  natural  toughness  and  elasticity  of  the  paint  still 
remained. 

It  will  be  noted  that  there  is  a  wide  discrepancy  in  the  results 
of  the  dish-test  of  Mr.  Toltz,  as  above,  of  the  graphite  paints,  both 
the  natural  amorphous  pigments  and  the  compounded  silica-graphite 
pigments,  and  the  plate- test  given  by  Professor  Smith  of  pure  flake- 
graphite  mixed  with  raw  linseed-oil  that  gave  215  pounds  of  corrosion 
to  1500  square  yards.  This,  no  doubt,  is  due  to  the  repellent  nature 
of  the  pure  flake-graphite;  the  pigment  does  not  take  kindly  to  the  oil, 
any  more  than  soapstone  does.  Raw  oil,  even  if  pure,  contains  from 
5  to  7  per  cent  of  water,  that  renders  a  combination  of  the  graphite 
and  oil  quite  uncertain  unless  under  the  influence  of  heat.  The  boiled- 
oil  vehicle  with  pure  flake-graphite,  used  by  Professor  Spennrath  in 
his  experiments  (hereafter  referred  to)  with  paintrskins  detached 
from  the  metal  surfaces,  withstood  an  exposure  in  a  pure  water-bath 
for  six  weeks  without  injury  other  than  a  slight  loss  in  weight  of  the 
skin.  Moisture  in  the  oil  in  this  case  was  eliminated,  as  in  the  case 


286  FERRIC-PAINT   TESTS. 

of  Mr.  Toltz's  graphite  paints,  and  the  merits  of  boiled  oil  as  a  vehicle 
for  most  paints  over  raw  oil  is  sustained  in  these  experiments,  as  it  is 
in  daily  practice  elsewhere. 

United  States  Navy-yard  Paint  Tests. 

The  result  of  these  tests  corroborate  the  series  of  tests  made  by 
order  of  the  Secretary  of  the  United  States  Navy  in  1884-5.*  By 
request,  sixty  paint  firms  submitted  seventy-five  different  paints  for 
test,  which  were  applied  to  five  hundred  test-plates,  and  then  im- 
mersed in  sea- water  at  four  navy-yards,  and  upon  one  government 
vessel  in  service.  The  paints  that  successfully  withstood  the  test 
and  received  an  order  of  merit,  were  red  lead,  zinc  oxide,  carbon,  and 
graphite  compounds.  The  so-called  asphaltum  paints  were  at  the 
bottom  of  the  list  in  the  no-merit  column.  Evidently  there  has  been 
slight  improvement,  if  any,  in  this  class  of  paints  since  the  date  of 
the  U.  S.  Navy  tests  to  the  present  time,  and  one  can  but  wonder, 
in  the  face  of  repeated  and  recorded  failures,  that  they  ever  receive 
an  application  to  a  ferric  structure,  ashore  or  afloat.  Lead,  zinc, 
carbon,  and  graphite  compounds  maintain  their  supremacy  for  gov- 
ernment work.  In  other  tests  of  commercial  and  special  paints, 
where  the  tests  have  been  carried  to  the  destruction  of  the  coating 
as  a  whole,  the  partial  destruction  of  the  vehicle  was  generally  fol- 
lowed by  the  disintegration  of  the  weaker  substances  comprising 
the  pigment,  such  as  the  carbonate  and  sulphate  of  lime,  asphaltum, 
iron  oxide,  and  the  various  color  pigments,  viz.,  the  ochres,  umbers, 
blues,  greens,  carmines,  yellows,  etc.  The  only  pigments  practically 
unaffected  by  the  destructive  element  were  the  graphites,  the  silica, 
barytes,  slag,  slate,  and  brickdust.  Other  adulterants  were  but  little 
affected,  some  of  them  being  partly  recoverable,  which  was  also  the 
case  with  the  red  lead,  white  lead,  and  zinc-oxide  pigments. 

Commercial  Coal-tar  Paints. 

Fourteen  commercial  paints,  principally  of  the  coal-tar  and  asphalt 
class,  were  tested  under  uniform  conditions,  viz:  Wrought-iron 
plates,  free  from  mill-scale,  were  coated  with  two  coats  each  of  the 
following  paints.  All  of  the  coatings  were  perfectly  dry  before  the 
second  coat  was  applied.  When  the  second  coats  were  dry  and 

*  Transactions  American  Society  Mechanical  Engineers,  1894,  Vol.  XVI, 
Paper  No.  625,  pp.  399-402. 


FERRIC-PAINT  TESTS.  287 

hard,  one  set  of  the  plates  was  immersed  for  two  months  in  sea-water, 
and  another  set  was  exposed  to  atmospheric  influences,  where  com- 
bustion gases  from  locomotives  and  coke  ovens  reached  them  freely 
at  all  times,  this  exposure  being  similar  in  all  respects  to  that  of  rail- 
way-bridge paints.* 

No.  1.  Carbonizing  coating  (Cohen  Mfg.  Co.). 

Physical  properties. — Very  black,  good  body,  spread  well,  and 
covered  a  large  surface,  coating  smooth. 

Drying  properties. — Poor. 

After  24  hours,  wet. 
"48       "      quite  wet. 
"72       "      slightly  wet. 
"96       "      dry. 

Physical  test. — In  sea-water,  much  rusted  and  blistered,  paint 
easily  rubbed  off,  and  in  bad  condition.  Atmospheric  exposure, 
condition  of  coating,  fair. 


No.  2.  Durable  metal  coating  (Edward  Smith  &  Co.). 
Physical  properties. — Brownish  color,  thin  and  required  a  large 
quantity  to  cover;  adhered  poorly;   coating  thin  and  uneven. 
Composition. — Linseed-oil,  asphaltum,  and  kauri-gum 
Drying  qualities. — Dried  slowly. 

After  24  hours,  wet. 

"48       "      tachy. 

"     72       "      slightly  tachy. 

"96       "      dry. 
Second  coat  dry  in  7  days. 

Physical  tests. — In  sea-water,   much    rusted,    peeled    off    easily, 
and  blistered. 

Atmospheric  exposure. — Rusted  badly  on  edges  of  the  plate. 


No.  3.  Turpentine  asphaltum  (C.  A.  Reeves  &  Co.). 
Physical    properties. — Coating    thick    and    uneven;     required    a 
large  amount  to  cover.     Spread  poorly;  adhered  well. 

*  Transactions  American  Society  Mechanical  Engineers.     Experiments  by 
J.  H.  Pennock,  Chemist.     Vol.  XXII,  1900,  1901,  Paper  No.  901. 


288  FERRIC-PA  INT_  TESTS. 

Drying  properties. — 


After  24  hours,  quite  wet. 
"48       "      tachy. 
"72      "      almost  dry. 
"84       "      dry. 


Physical  test. — In  sea-water,  much  rusted,  paint  peeled  off  in 
spots;  did  not  rub  off  as  easily  as  No.  2.  In  two  spots  corrosion 
had  eaten  through  the  plate. 

Atmospheric  exposure. — Condition  very  bad,  rusted  all  over. 


No.  4.  "B."  Black  varnish  (Mica  Roofing  Co.). 
Composition. — A  coal-tar  product,  contained  light  oils,  naphtha- 
lene and  anthracene,  not  indicating  much  pitch. 

Physical  properties. — Very  fluid,  gave  a  smooth  coating. 
Drying  properties. — 

After  24  hours,  wet. 

"48       "  quite  wet. 

"72      "  slightly  wet. 

"96       "  dry. 

Physical  test. — In  sea-water,  fairly  free   from  rust,  but  coating 
was  rough  and  uneven,  broken  off  in  many  places. 

Atmospheric  exposure. — Rusted  badly  along  the  edges. 


No.  5.  Asphaltum  paint  (C.  E.  Mills  &  Co.). 

Composition. — Asphaltum,  petroleum,  and  some  linseed-oil. 

Physical  properties. — Thickens  on  exposure  to  air;  gives  a  thick 
uneven  coat. 

Drying  properties. — Dry  in  56  hours. 

Physical  test. — In  sea-water,  much  rusted  and  blistered,  large 
part  of  the  plate  coating  entirely  gone. 

Atmospheric  exposure. — Plate  in  very  bad  condition. 


No.  6.  Black  diamond  paint  (C.  W.  Reeves  &  Co.). 
Composition. — Pitch  and  dead  oil. 

Physical  properties. — Quite  fluid,   spread  well  and  adhered  well 
and  gave  a  good  even  coating;  smells  of  coal-tar. 


FERRIC-PAINT  TESTS.  289 

Drying  properties. — 

After  24  hours,  slightly  tachy. 
"     36       "      almost  dry. 

I  (          JO  (  (  (I  (I 

"60       "      dry. 

Physical  test. — In  sea-water,  did  not  blister,  rusted  considerably, 
paint  off  in  spots.  Not  so  good  condition  as  No.  4,  but  better  than 
Nos.  1,  2,  3,  and  5. 


No.  7.  "A."  Varnish  (Mica  Roofing  Co.). 
Composition. — Asphaltum,  in  petroleum  spirits. 
Physical  properties.— Fluid,  spreads  well  and  adheres  well;   gave 
a  thick  coating  fairly  smooth,  smells  strongly  of  petroleum  spirits. 
Drying  properties. — 

After  24  hours,  quite  wet. 
"48       "      slightly  tachy. 
"60       "      dry. 

Physical  test. — In  sea-water,  much  rusted,  not  blistered,  paint  off 
in  numerous  spots.     In  bad  condition. 
Atmospheric  exposure. — Badly  rusted. 


No.  8.  Mineral  rubber  (Assyrian  Asphalt  Co.). 

Physical  praperties. — This  paint  was  so  thick  and  viscous  that 
it  could  not  be  applied  without  thinning.  When  thinned  with  naphtha 
it  did  not  work  satisfactorily,  and  the  experiments  with  it  were  aban- 
doned. (See  Chapter  XII.) 


No.  9.  Black  roofing  paint  (Samuel  Cabot). 

Composition. — Pitch  dissolved  in  light  petroleum  oil. 

Physical  properties. — Fluid,  gave  a  smooth  coating  that  adhered 
well.  Smelt  of  tar-oil. 

Drying  properties. — Dried  in  56  hours. 

Physical  tests. — In  sea-water,  rusted  badly,  coating  off  in  many 
spots,  rubbed  off  easily. 

Atmospheric  exposure. — Rusted  badly  all  over. 


290  FERRIC-PAINT  TESTS. 

No.  10.  Black  paint  (Thomas  Mfg.  Co.). 

Composition. — A  coal-tar  paint  with  a  heavy  oil  menstruum. 

Physical  properties. — Much  like  No.  9. 

Drying  properties. — 

After  24  hours,  wet. 

"48       "      tachy. 

"     60       "      dry. 

Physical  tests. — In  sea-water,  paint  came  off  easily;   many  rust- 
spots. 

Atmospheric  exposure. — Condition  fairly  good. 


No.  11.  Slag  cement  paint  (Barrett  Mfg.  Co.). 

Physical  properties. — A  coal-tar  paint,  producing  a  coating  similar 
to  Nos.  9  and  10. 

Drying  properties. — Dry  in  60  hours. 

Physical  tests. — In  sea-water,  had  a  tendency  to  peel  off;  some 
rust-spots  noticed. 

Atmospheric  exposure. — Plate  badly  rusted. 

No.  12.  "Ferrodor"  (Wm.  Somerville's  Sons). 

Composition. — Graphite,  turpentine,  oxide  of  iron,  and  linseed-oil. 
A  compound  or  patent  paint. 

Physical  properties. — Color,  purplish  gray;  coating,  very  thin; 
three  coats  recommended  by  the  manufacturers. 

Drying  properties. — Dry  after  48  hours. 

Physical  tests. — In  sea-water,  paint  peeled  off  badly,  plates  very 
much  corroded,  bad  condition  generally.  The  graphite  settled  to 
the  bottom  of  the  can  in  a  tenacious  pasty  mass,  and  the  paint  was 
spread  with  great  difficulty. 

No.  13.  "Antoxide."    Ready  mixed  paint  (Harrison  Bros.). 

Physical  properties.—  Bright-red  color  due  to  red  lead;  very 
fluid;  spread  well,  giving  a  smooth  even  coating  that  adhered  well. 

Drying  properties. — Dry  after  48  hours. 

Physical  properties. — In  sea-water  corroded  badly,  paint  peeled 
off,  plate  much  rusted. 

Atmospheric  exposure. — Paint  turned  black,  plate  badly  rusted 
and  scaled  off. 


FERRIC-PAINT   TESTS  (BAKER'S). 


291 


No.  14.  "Crysolite"  (Solvay  Process  Co.). 

Composition. — A  paint  made  from  coal-tar  (special  process). 

Physical  properties. — Deep-black  color;  spread  well  and  adhered 
well,  giving  a  smooth  even  coating,  rather  thick;  contained  10  per 
cent  free  carbon. 

Drying  properties. — Dry  in  36  hours. 

Physical  tests. — In  sea-water  no  corrosion  or  blistering;  had  a 
slight  tendency  to  peel. 

Atmospheric  exposure. — Plate  slightly  rusted;  stood  the  action 
of  combustion  gases  better  than  any  of  the  other  competitive  paints. 
There  was  no  tendency  of  the  paint  to  run  or  crawl  when  applied  to 
any  metallic  surface  at  ordinary  temperature.  (See  Water-pipe 
Coatings,  Chapter  XII.) 

A  number  of  commercial  ferric  paints  were  tested  (1899)  by 
Prof.  Ira  O.  Baker  for  their  comparative  resistance  to  heat,  sea- 
water,  strain,  elasticity,  the  fumes  of  sulphuric  and  nitric  acids 
also  carbonic  acid,  with  the  following  results:* 

The  samples  of  paint  named  were  furnished  by  the  manufacturers 
for  the  purpose  and  mixed  with  linseed-oil  as  directed  by  them,  and 
spread  on  clean  bright  wrought-iron  test-plates. 


Reference 
Number. 

Kind  of  Paint. 

Weight  per 
Gallon. 

How  Received  from  the  Maker. 

1 

Red  lead                

Pounds. 
31    72 

Dry  pigment. 

2 

White  lead          

21  24 

Paste. 

3 

Purple  iron  oxide  

11.34 

Mixed  ready  for  use. 

4 
5 

6 

7 

Chattanooga  iron  oxide  
Williamsport  iron  oxide  
Detroit  superior  graphite.  .  .  . 
Mexican  graphite     

14.13 
12.99 
9.49 

8.57 

Dry  pigment. 

Mixed  ready  for  use. 

«          u  "    a      u 

Drv  pigment. 

8 

Dixon's  graphite               

8.84 

Mixed  ready  for  use. 

9 

Trinidad  asphalt       

9.52 

«                      K             «             H 

10 

Bessemer  paint             

13.09 

it                  U          (t          H 

11 

Carbonizing  coating  

9.61 

It            ft       ft       tt 

12 

Lithogen  silicate           

17.06 

Paste. 

A  sample  of  each  paint  in  one  and  two-coat  work  was  exposed 
to  heat  and  the  products  of  combustion  in  the  smoke-flue  from  a 
boiler  burning  bitumnous  coal.  The  condition  of  the  plates  on 
removal  was: 

1.  Red  lead. — Entirely  dead  and  very  brittle.  The  powdery  resi- 
due was  easily  removed,  bringing  into  view  the  base  metal. 


*  Railroad  Gazette  (New  York),  March  10,  1899. 


292  FERRIC-PAINT  TESTS  (BAKER'S). 

2.  White  lead. — Blistered  and  baked.     Coating  was  brittle  and 
entirely  dead,  and  very  easily  removed.     Removal  of  the  residue 
exposed  the  base  metal. 

3.  Purple    iron  oxide. — Covered   with   blisters.     Paint   soft   and 
easily  removed.     Removal  of  the  blisters  exposed  the  base  metal  only 
to  a  slight  extent. 

4.  Chattanooga   iron  oxide. — Considerably  blistered,   moderately 
soft,  adhering  well.     Removing  the  blisters  did  not  expose  the  base 
metal. 

5.  Williamsport  iron  oxide. — Covered  with  blisters.     Paint  tena- 
cious, adhering  well.     Removing  the  blisters  exposed  the  base  metal. 

6.  Superior  graphite. — Small  blisters.     Paint  hard  and  difficult 
to  remove.     Almost  impossible  to  expose  the  base  metal. 

7.  Mexican  graphite. — Soft  and  readily  removed.     Removal  of 
blisters  did  not  expose  the  base  metal. 

8.  Dixon's  graphite. — Very  few  blisters.     Paint  hard  and  very 
adherent. 

9.  Trinidad  asphalt. — Smooth;  considerable  of  the  paint  melted 
and  ran  off.     The  portion  remaining  was  hard  and  brittle. 

10.  Bessemer  paint. — Soft  and  hard  to  scratch  off. 

11.  Carbonizing  coating. — Ridges  very  conspicuous.     Paint  firm 
and  adherent.     Removal  of  blisters  exhibited  a  very  porous,  loose 
structure  of  the  paint. 

12.  Lithogen  silicate  (white  paint). — Substantially  the  same  as 
the  white  lead. 

Effect  of  salt  water. — A  set  of  the  plates  were  exposed  to  a  satu- 
rated solution  of  sea-salt  (brine)  for  seven  weeks,  the  plates  being 
frequently  withdrawn  and  allowed  to  dry.  Their  condition  at  the 
end  of  the  exposure  was: 

1.  Red  lead. — Hard  and  adhering.     Metal  clean  and  bright  under 
the  two  coats,  but  badly  rusted  under  the  single  coat. 

2.  White  lead. — Hard  and    adhering.     Clean    metal    under    two 
coats,  rust  under  the  single  coat. 

3.  Purple  iron  oxide. — Firm  and  adhering.     Occasional  rust-spots 
throughout. 

4.  Chattanooga  iron  oxide. — Firm  and  adherent.     No  rust  any- 
where. 

5.  Williamsport  iron  oxide. — Firm,  and  adhered  only  fairly  well. 
Metal  under  two  coats  bright,  but  under  the  single  coat  considerable 
rust. 


FERRIC-PAINT  TESTS  (BAKER'S).  293 

6.  Detroit  superior  graphite. — Hard  and  adhering  well.      Rust 
under  the  single  coat,  none  under  two  coats. 

7.  Mexican  graphite. — Elastic  and  easily  removed.     No  rust. 

8.  Dixon's   graphite. — Good   condition.     Elasticity   only   slightly 
impaired.     Easily  removed    no  rust. 

9.  Trinidad  asphalt. — Seemingly  unaffected.     No  rust  anywhere. 

10.  Bessemer  paint. — Moderately  hard,  peeled  off  easily,  no  rust. 

11.  Carbonizing  coating. — Peeled  off  easily.     Rust  beneath  both 
the  one  and  two  coats. 

12.  Lithogen  silicate. — Hard  and  adherent.     No  rust-spots. 

No  report  was  made  of  the  condition  of  the  paints  exposed  to 
atmospheric  influences,  evidently  for  the  reason  that  the  exposure 
period  had  riot  been  long  enough  to  materially  affect  any  of  the 
paints  when  the  test  closed. 

A  set  of  the  plates  were  exposed  to  the  fumes  of  strong  sulphuric-, 
nitric-,  and  carbonic-acid  gases  for  five  weeks.  The  action  of  the  sul- 
phurous gas  was  characterized  by  its  bleaching  power  upon  the  paints 
and  the  disintegrating  effect  on  the  iron  under  the  paint,  also  the 
formation  over  the  entire  area  of  blisters,  under  which  was  found  a 
moderately  hard  whitish  deposit. 

The  order  of  merit  for  the  several  paints  was :  Trinidad  asphaltum, 
Carbonizing  coating,  Dixon's  graphite,  Red  lead,  Lithogen  silicate, 
Mexican  graphite,  Purple  iron  oxide,  Superior  graphite,  Bessemer 
paint,  Chattanooga  iron  oxide,  Williamsport  iron  oxide,  White  lead. 

The  effect  of  the  nitric-acid  gas  was  substantially  the  same  as  the 
sulphurous  gas,  except  that  the  single  coatings  of  the  paints  were 
completely  destroyed.  The  order  of  merit  for  the  double  coatings 
was:  Trinidad  asphaltum,  Lithogen  silicate,  Red  lead,  White  lead, 
Purple  iron  oxide,  Superior  graphite,  Mexican  graphite,  Chattanooga 
iron  oxide,  Williamsport  iron  oxide,  Dixon  graphite,  Carbonizing  coat- 
ing, Bessemer  paint. 

The  carbonic-acid  gas  in  large  quantities,  supplemented  by  mois- 
ture, had  only  an  almost  imperceptible  effect  upon  any  of  the  paints. 

To  test  whether  any  of  the  paints  would  crack  during  the  elonga- 
tion of  a  painted  bar,  strips  of  machine  steel  2"Xi"Xl8"  were  painted 
two  coats,  and  after  drying  for  two  months  were  submitted  to  a  strain 
of  16,000  pounds  per  square  inch;  the  paint  in  every  case  remained 
firm  and  close-adhering.  The  stresses  were  then  increased  slowly 
beyond  the  elastic  limit  of  the  steel,  and  in  no  case  did  the  paint 
crack  before  that  point  was  reached. 


294  FERRIC-PAINT  TESTS  (BAKER'S). 

It  was  noticed  that  after  passing  the  elastic  limit  of  the  steel, 
the  paints  were  marked  by  a  series  of  lines  arranged  in  herring- 
bone patterns,  that  were  alike  on  both  sides  of  the  bar  and  alike 
situated.  Evidently  the  lines  were  due  to  a  rearrangement  of  the 
.atoms  of  the  steel  bars  while  under  strain,  the  centre  atoms  moving 
less  freely  than  those  near  the  corners  and  edges  of  the  bars,  the 
paint  naturally  following  the  particles  of  steel  that  they  covered. 
Naturally  the  heavier  coatings  of  the  paints  were  the  least  elastic. 
The  order  of  merit  in  the  elasticity  test  was:  Trinidad  asphaltum, 
Carbonizing  coating,  Purple  iron  oxide,  Dixon  graphite,  Mexican 
graphite,  Superior  graphite,  Williamsport  iron  oxide,  Chattanooga 
iron  oxide,  Bessemer  paint,  White  lead,  Red  lead,  Lithogen  silicate. 


CHAPTER  XXX. 


PAINT   TESTS   ON   RAILWAYS. 

New  York  Elevated  Railways. 

THE  physical  condition  and  the  extent  of  corrosion  on  all  parts 
of  these  structures  have  been  freely  commented  upon  by  the  technical 
engineering  journals  and  the  daily  press.  When  originally  erected, 
no  attempt  was  made  to  remove  the  mill-scale,  and  none  has  been 
made  since,  presumably  because  of  the  impossibility  of  its  success, 
and  the  cost.  The  composition  of  the  paint  which  has  been  repeatedly 
applied  to  them  has  been  kept  very  uniformly  good  in  quality,  but  its 
application  has  been  solely  for  appearance,  as  no  paint  can  now  reach 
the  seat  of  corrosion  underlying  all  the  coats  of  scale,  dust,  cinders, 
and  paint. 

The  renewal  of  the  whole  structure  will  probably  be  necessary  in 
less  than  a  hundred  years  from  its  erection. 

The  composition  of  the  paint  used  is  given  by  the  chief  engineer 
as  follows: 

FOR  FIFTY  GALLONS  OF  PAINT,  OLIVE-DRAB  COLOR. 

Summer  Winter 

Formula.  Formula. 

White  lead,  Jewett's  best 300  pounds  275    pounds 

Bridgeport  zinc  oxide,  strictly  best  quality 175      "  150        " 

French  ochre                        "           "         "     100      "  90 

Prussian  blue                       "           "         "     1      "  1        " 

Lampblack                                                                                  *  "  i     " 

576i  pounds   516i  pounds 

The  above  pigments  are  ground  in  Campbell  & 
Thayer's  raw  linseed-oil,  The  weights  given  include 
the  necessary  oil  to  grind  the  pigments  to  a  paste. 

When  applied,  it  was  mixed  with 

Boiled  linseed -oil,  Campbell  &  Thayer's 8  gall  9  gall 

Raw  linseed-oil,  "         "         «          15  15 

Spirits  of  turpentine,  first  quality 3      "  3      " 

Liquid  or  japan  drier,    "          "      3      " 

28  gall.  30  gall 

295 


296  PAINT   TESTS  ON  RAILWAY  STRUCTURES. 


New  York  Elevated  Railway  Viaduct. 

The  viaduct  over  the  Harlem  Station  of  the  New  York  Elevated 
Railway  at  155th  Street  was  oil-coated,  and  received  iron-oxide 
paint  coatings  at  the  time  of  its  erection,  and  within  five  years  of  its 
eompletion  had  developed  corrosion  to  such  an  extent  that  in  1897 
the  sand-blast  was  used  to  clean  it  preparatory  for  another  effort  for 
its  preservation.  This  sand-blast  process  cost  about  $10,000,  or  over 
fifteen  cents  per  square  foot  to  apply,  or  about  seven  times  more  than  a 
properly  selected  method  of  procedure  and  paint  would  have  cost  in 
the  first  place,  and  then  only  the  lower  and  accessible  sides  or  parts 
in  sight  received  treatment.  About  50,000  square  feet  of  surface  was 
cleaned  by  the  sand-blast,  to  the  bright  iron,  removing  about  12  tons 
of  old  paint,  scales  of  rust,  and  cinders,  showing  a  unmber  of  distinct 
layers  of  highly  corroded  matter. 

Seventeen  panels  of  lattice-truss,  floor-beam  and  buckle-plates, 
supporting  the  paved  carriage  roadway  and  footpaths  overhead, 
about  2825  square  feet  of  surface  each,  and  numbered  consecutively 
1  to  17,  were  then  painted  with  the  same  number  of  selected  protec- 
tive coatings  furnished  by  a  like  number  of  paint  firms  in  competition 
with  each  other.  The  several  coatings  were  applied  in  strict  con- 
formity to  the  directions  received  with  each  brand  of  paint,  the  appli- 
cation being  to  the  bright  iron  as  left  by  the  action  of  the  sand-blast, 
and  within  3  to  4  hours  from  the  time  the  sand-blast  ceased  action. 
Every  possible  condition  was  brought  into  bearing  to  make  the  test 
one  of  a  practical  and  commercial  nature  as  well  as  of  .scientific  value, 
absolutely  without  prejudice  or  favor  in  any  respect.  From  the 
prominence  of  the  structure  in  an  engineering  view,  and  its  situation 
exposed  to  storms,  sea  air,  fog,  cinders,  steam,  and  gases  from  scores 
of  locomotives  in  constant  service  beneath  it,  nearly  all  of  the  metal 
being  within  a  few  feet  of  the  tops  of  engine-stacks  and  receiving  the 
products  of  combustion  under  blast-action  and  in  an  approximately 
closed  space,  the  future  result  was  anxiously  looked  for  as  an  impor- 
tant demonstration  of  the  practical  value  of  the  several  best  pro- 
tective coatings  in  the  market. 

After  an  exposure  of  about  nine  months,  and  while  a  few  of  the 
coatings,  viewed  from  the  station  platform,  showed  slight  evidences 
of  failure,  a  thorough  examination  of  the  condition  of  each  panel 
was  made  by  a  prominent  civil  engineer  of  New  York  City.  This 


PAINT   TESTS  ON  RAILWAY  VIADUCTS. 


297 


report  is  of  extreme  interest,  and  is  summarized,  viz.,  100  rating  as 
perfect  condition  of  the  coating.* 


Number  of 
Panel. 

Number  of 
Coats  of 
Paint. 

Kind  or  Name  of  Paint. 

Rate  of 
Drying. 

Freedom 
from  Rust, 
Per  Cent. 

Reference 
Marks  as  to 
Condition. 

1 

3 

Lead,  graphite  and  lucol-oil  

Medium. 

97 

O. 

2 

2 
2 

Amorphous  graphite,  Detroit  Co.  —  L.S.G. 
Red  lead,  antoxide,  F.  and  D  

Slow 
Fast 

80 

25 

b 
c 

4 

2 

Graphite  (kind  not  stated)  

Slow 

75 

d 

5 

3 

Nobrac  (trade  mark) 

Medium 

99 

6 

7 
-    8 

2 
2 
2 

Carbon  Black  (F.  W.  Devoe  &  Co.)  
Durable  Metal  Coating  (E.  Smith's  varnish) 
Black  Manganese  (iron  paint)   

Slow 
Slow 
Fast 

85 
75 
30 

d 
d 
f 

Q 

2 

Carbonizing  Coating  (trade  mark)  

Slow 

80 

a 

10 

4 

Mineral  Rubber  (no  particulars)  

Fast 

78 

a 

11 

2 
2 

Black  varnish  (composition  not  given).  .  . 
Carbon  paint  (no  particulars)  

Medium 
Medium 

58 
92 

h 
a 

13 

2 

Graphite   (Standard  Oil  Co.).     Kind  not 
stated  .*  

Medium 

67 

a 

14 
15 

2 
2 

Dixon  Co.  Silica  graphite,  mixed  paint  .  .  . 
Asphaltum  (California  Co.  brand)  

Slow 
Very  Slow 

70 
65 

d 

16 

2 

Ruberine  (trade  mark).     Coal-  tar  compo- 
sition 

Medium 

58 

k 

17 

2 

Black  diamond  (trade  mark) 

Medium 

70 

I 

a.  Very  little  rust.     Paint  crumbles  in  places  as  though  rotten.     Easily  re- 
moved. 

b.  Fair  condition,  but  discolored;   rust  coming  through. 

c.  Very  badly  rusted. 

d.  Rusty,  but  not  deep. 

e.  Slight  rust  on  top  flange  of  one  girder;  rest  of  girder  clean. 
/.  Rust  very  deep ;   buckle  plates  bad. 

g.  Area  of  rust-spots  small;   rust  not  very  deep. 

h.  Rust  very  bad  and  deep. 

/.  Deeply  rusted ;  buckle  plates  still  good. 

k.  Rust  very  deep  and  angry ;  buckle  plates  mildewed. 

I.  Small  pimples  of  rust,  as  though  formed  under  the  paint. 

Panel  No.  1  was  an  outside  one,  and  the  first  to  be  sand-blasted 
and  painted,  in  some  parts  with  two  and  in  others  three  coats  of 
paint,  in  the  clear  hot  days  of  summer,  a  material  advantage  in  its 
favor.  The  sand-blast  was  then  shifted  to  the  southern  end  of  the 
viaduct;  and  panel  No.  17,  also  an  outside  one,  was  the  next  one 
cleaned  and  painted  in  hot  clear  weather,  and  so  on  consecutively,  in 

*  Engineering  News,  September  23,  1897,  Illustrated;  Engineering  Record, 
September  25,  1897,  Illustrated. 


298  PAINT  TESTS  ON  RAILWAY    VIADUCTS. 

the  reverse  order  of  the  panel  numbers,  back  to  No.  1 ;  panels  Nos.  7 
to  2  having  been  done  late  in  the  fall  under  unfavorable  conditions 
as  to  the  spreading  and  drying  of  the  paint  in  addition  to  the  other 
objectionable  conditions.  About  80  square  feet  of  panel  surface 
was  cleaned  per  hour,  or  600  square  feet  per  working  day;  each 
panel  requiring  from  five  to  six  days  to  clean  and  paint  it. 

At  the  end  of  about  a  year  the  condition  of  all  of  the  paints  was  so 
unsatisfactory  that  the  viaduct  was  repainted  without  removing, 
only  in  a  perfunctory  manner,  the  old  test  coatings  with  their 
fast-forming  burdens  of  rust;  and  this  competitive  test  came  to  an 
inglorious  end. 

The  result  could  have  been  foreseen  from  the  first,  before  a  single 
truss  or  pound  of  material  had  been  placed  in  position,  or  was  even 
out  of  the  construction  shops,  had  not  commercial  greed,  official 
indifference  or  ignorance,  either  one  or  all,  ruled  the  matter. 

The  destruction  of  the  tubular  railway  bridge  over  the  St.  Law- 
rence River  at  Montreal,  Canada,  had  not  become  a  fact  so  musty 
with  age  as  to  have  escaped  attention  concerning  the  dangerous  effect 
of  hot  combustion  gases  upon  any  paint  coating  in  a  confined  space. 
Corrosion  history  blindly  repeated  itself  when  the  viaduct  material 
was  first  painted  by  the  contractors,  then  repeated  the  "Comedy 
of  Errors"  when  it  was  erected  and  again  when  it  was  sand-blasted 
for  its  final  fiasco.  The  plain  facts  of  the  painting  after  the  sand 
blast  action  are,  that  the  coat  ngs  were  destined  for  an  early  destruc- 
tion from  the  beginning,  by  reason  that  the  first  coat  was  applied  in 
an  atmosphere  saturated  with  the  hot  vapors  of  combustion  and 
steam,  which  were  so  corrosive  that  the  freshly  cleaned  surface  of 
the  metal  showed  a  blush  of  rust  within  an  hour  after  cleaning,  and 
if  left  for  three  hours  the  rust  could  be  wiped  off  by  the  hand.  The 
paints  were  spread  in  this  atmosphere,  and  before  they  could  in 
any  measure  dry,  so  as  to  be  in  any  degree  resisting,  they  were  thor- 
oughly impregnated  by  the  hot  gases  and  steam  which  left  their  con- 
densed strength  upon  the  surfaces  of  the  green  paints.  The  second 
and  subsequent  coats  were  not  only  applied  under  the  same  atmos- 
pheric conditions  as  to  the  hot  vapors  and  cinders,  but  had  the 
condensed  products  of  combustion  sandwiched  between  them. 
Probably  a  baked  japan  or  Bower-Barff  coating  are  the  only  ones 
which  would  have  successfully  met  the  situation,  which  is  an  excep- 
tional one.  Such  coatings  applied  at  first,  would  not  have  cost  one- 
half  as  much  as  the  sand-blast  and  the  several  coatings  applied  in 


PAINT   TESTS  ON  RAILWAY  VIADUCTS.  299 

the  first  and  subsequent  stages,  and  would  have  been  thoroughly 
protective  and  avoided  nearly  all  the  future  expense  in  the  care  of 
the  structure  so  far  as  the  painted  surfaces  are  concerned. 

A  paint  test  of  an  extended  character  has  been  in  progress  for 
the  past  few  years  by  Mr.  Geo.  W.  Webster,  C.E.,*  to  determine 
the  best  paints  for  use  on  the  city  street  iron  bridges,  crossing  the 
railroads  within  the  city  limits  of  Philadelphia,  Pa. 

Fifty-four  sample  plates  of  iron  12"X24"  were  coated  by  twenty- 
two  manufactures  of  paint,  and  exposed  at  a  number  of  places  on 
the  street  viaducts,  in  situations  that  were  as  nearly  uniform  for  the 
several  competitive  coatings  as  possible  to  provide.  The  test  coat- 
ings were  changed  in  their  location  as  circumstances  required  to 
equalize  the  exposures,  which  were  very  severe,  the  clearance  between 
the  top  of  the  locomotive  stacks  and  the  metal  work  of  the  bridges 
being  only  two  to  three  feet. 

The  samples  of  paint  submitted  included  the  most  prominent 
proprietary  paints,  including  the  carbon  and  graphite  classes. 

The  results  of  only  a  few  months'  test  demonstrated  that  on  the 
lower  surfaces  of  the  plates  on  the  bridge  structure  no  paint  was 
able  to  resist  the  mechanical  injury  from  the  sand-blast  action  of 
the  locomotive  exhaust.  These  situations  are  now  protected  from 
this  action  by  wooden  sheeting  a  few  feet  in  width  on  the  line  of  the 
exhaust. 

On  the  upper  side  of  the  test-plates,  subject  to  moisture,  com- 
bustion gases,  and  deposits  of  cinder,  the  results  were  more  satisfac- 
tory, but  were  not  conclusive  as  to  the  relative  merits  of  the  samples, 
due  to  the  difficulty  in  comparison  on  the  basis  of  truly  identical 
conditions. 

The  general  trend  of  the  results  was,  the  subsequent  selection  of 
certain  of  the  proprietary  paints  for  a  trial  on  bridges,  and  component 
parts  of  bridges,  under  a  general  formula,  having  red  lead  as  the 
principal  pigment,  viz: 

Red  lead,  two  coats  over  shop  coat  of  raw  linseed-oil  for  inclosed 
space  of  structures. 

Red  lead  over  shop  coat  of  raw  linseed-oil  and  two  coats  of  white 
lead  three  parts,  and  zinc  oxide  one  part,  for  the  field  work. 

Indian  red,  one  coat  over  shop  coat  of  oil.     Red  lead,  third  coat. 

*  Chief  Engineer's  Bureau  of  Surveys,  Department  of  Public  Works,  City  of 
Philadelphia,  Pa.,  1902. 


300  PAINT   TESTS  ON  RAILWAY   VIADUCTS. 

Indian  red,  one  coat  over  shop  coat  of  oil.  White  lead  three 
parts,  zinc  oxide  one  part,  for  field  work. 

The  Gray's  Ferry  deck  bridge  over  the  Schuylkill  River  was  in- 
cluded in  the  test,  being  painted  with  the  following  paints,  all  applied 
as  a  first  or  shop  coat : 

Nobrac,  lucol-oil  paint,  rubber  paint,  Bessemer  paint,  antoxide, 
durable  metal  coating,  red  lead.  Above  the  deck  for  the  second  full 
coat,  red  lead  was  applied,  except  in  one  case,  where  white  lead  and 
zinc  oxide  were  used.  Below  deck,  for  the  third  full  coat,  the  same 
paint  was  used  as  for  the  shop  coat,  except  in  one  case  where  white 
lead  and  zinc  oxide  were  used  for  both  the  second  and  third  coats. 

The  above  coatings  were  applied  in  1899-1900,  and  the  time 
since  then  has  been  too  short  to  note  any  material  difference  in  their 
condition.  The  general  practice  in  painting  ferric  structures  by 
the  Board  of  Public  Works  of  the  city  of  Philadelphia  for  a  number  of 
years  has  been  the  use  of  red  lead  and  lampblack  for  a  first  or  prim- 
ing coat  at  the  shop,  followed  by  two  coats  of  the  same  paint  in  dif- 
ferent shades  of  chocolate  color  for  the  field  coats,  though  in  some 
cases  white  lead  and  zinc  oxide  have  been  the  field  coats.  That  the 
above  paints  have  not  proven  satisfactory  in  the  presence  of  com- 
bustion gases  and  other  influences  incident  to  their  location  is  evi- 
dent from  the  above  experiments  to  correct  their  deficiencies.  In 
connection  with  the  same  matter,  it  may  be  of  interest  to  note  that 
the  train-shed  roof  of  the  Broad  Street  Station  of  the  Pennsylvania 
Railroad  at  Philadelphia,  which  was  painted  with  red  lead  and  lamp- 
black, is  seriously  affected  by  the  corrosion  of  the  roof-trusses.  This 
structure  has  had  extremely  good  care  since  its  erection;  but  corro- 
sion has  established  itself,  owing  to  the  early  decay  of  the  red-lead 
coatings,  and  will  soon  require  cleaning  by  the  sand-blast  to  correct 
the  mistake  of  using  red  lead  for  train-shed  painting.  (See  Chapter 
XXXVI,  Changes  in  Pigments.) 

Influences  that  Affect  Paints. 

Some  of  the  influences  that  affect  the  life  of  a  paint  coating  have 
been  determined  by  the  experiments  of  Prof.  J.  Spennrath,*  from 
whose  essay  the  following  excerpts  are  selected.  The  experiments 
were  made  upon  paint-skins  alone,  not  upon  a  painted  surface.  .The 
skins  were  made  from  chemically  pure,  finely  ground  flake  graphite 

*  "Protective  Coverings  for  Iron."     Railroad  Journal,  Xew  York,  1896. 


PAINT   TESTS.     SPENNRATH'S  EXPERIMENTS.  301 

and  linseed  oil,  applied  to  zinc  plates  in  two  coats,  each  of  which 
was  allowed  to  harden  thoroughly.  The  plates  were  then  placed  in  a 
dilute  solution  of  sulphuric  acid  and  the  zinc  dissolved.  The  paint- 
skins  were  then  used  for  testing  by  immersion  and  exposure  for 
six  months  in  a  number  of  liquids  and  gases,  as  follows : 

Immersion  Tests. 

In  pure  rain-water  the  skin  remained  cohesive, 
even  elastic,  was  of  dull  color,  noticeably  injured,  and 
lost  in  weight 10.4  per  cent. 

In  sea  water  the  skin  remained  uninjured  in  tex- 
ture and  lustre,  with  a  small  loss  in  elasticity,  and  in 
weight 4.52  "  " 

In  a  10  per  cent  solution  of  common  salt  the 
skin  was  but  little  affected  in  lustre  and  elasticity, 
but  lost  in  weight 2.4  "  " 

In  a  10  per  cent  solution  of  sal-ammoniac  the 
skin  was  unchanged.  Lost  in  weight 3.5  "  " 

In  a  5  per  cent  solution  of  sulphuric  acid  the  skin 
remained  unchanged.  Lost  in  weight 1.65  "  " 

In  a  twenty-four-hour  immersion  in  hot  water 
160°  to  170°  F.  the  skin  was  materially  affected  in 
texture  and  color.  Lost  in  weight .  9.83  "  " 

In  an  aqueous  solution  (alkaline)  of  mineral-coal 
ashes  the  skin  was  materially  affected.  Lost  in 
weight 14.8  "  " 

In  a  1  per  cent  solution  of  soda  the  skin  after 
three  days  was  vividly  affected,  and  after  a  few  days, 
more  exposure  was  destroyed. 

In  a  5  per  cent  solution  of  nitric  acid  the  skin 
was  destroyed. 

In  a  10  per  cent  solution  of  the  chloride  of  mag- 
nesium the  skin  was  unchanged,  but  lost  in  weight  1.1  "  " 

Exposure  Tests  in  Closed  Vessels. 

Over  sea-water  for  six  months  the  skin  was  unin- 
jured in  color  or  texture,  but  had  become  somewhat 
viscous;  no  loss  in  weight. 

Over  dry  chloride  of  calcium  (anhydrous)  the  skin 
was  not  at  all  affected,  and  gained  in  weight 0.46  "  " 


302  PAINT  TESTS.     SPENNRATH'S  EXPERIMENTS. 

Over  acetic  acid,  fuming  muriatic  acid,  nitric  acid, 
ammoniacal  liquor,  liquid  sulphate  of  ammonium, 
a  solution  of  gaseous  sulphurous  acid  and  water,  all 
the  skins  were  destroyed  in  a  few  days. 

A  skin  made  from  red  lead  and  linseed  oil,  exposed 
for  forty-eight  hours  to  an  atmosphere  of  hydric 
sulphide,  became  black  and  rough,  dull  in  lustre,  and 
increased  in  weight 1.5  per  cent. 

The  changes  here  indicated  relate  solely  to  the  vehicle,  as  the 
graphite  pigment  was  passive  to  the  action  of  any  of  the  destruc- 
tive agents.  Wherever  the  skins  were  destroyed  every  other  oil- 
paint  coating  would  have  been  likewise  destroyed,  whatever  pig- 
ment was  in  it.  In  the  other  cases  where  changes  in  the  vehicle 
are  noted,  the  change  of  the  skin  appears  to  be  wholly  unlike  that 
which  would  have  occurred  had  it  been  attached  to  any  surface. 
The  professor  has  evidently  found  this  to  be  the  case,  judging  from 
some  of  his  notes  preceding  the  record  of  his  tests.  There  are 
commercial  paints — notably  those  made  from  amorphous  mineral 
graphite,  that  containing  less  graphitic  carbon,  and  combined  with 
silica  and  a  small  amount  of  mineral  oxides — that  would  have  afforded 
a  better  protection  to  the  vehicle  than  the  chemically  prepared 
graphite  used  in  these  experiments,  the  cost  of  which  would  prob- 
ably bar  it  from  forming  any  part  of  a  protective  covering  for  iron. 

Spennrath's  Temperature  Tests. 

A  number  of  graphite  paint-skins  of  the  same  character  as  those 
used  in  the  above  immersion  and  exposure  tests;  also,  some  three- 
coated  skins  made  with  other  pigments  and  linseed  oil  and  mixed 
with  turpentine  and  other  driers,  and  mineral  oil,  were  submitted 
to  constant  temperatures  of  122°,  203°,  and  248°  F.  for  five  days. 
Briefly  the  results  were: 

All  the  skins  shortened  from  1.2  to  4.3  per  cent,  averaging  3.76 
per  cent,  and  lost  in  weight  from  2.11  to  8.3  per  cent,  averaging 
5.82  per  cent;  the  greatest  change  occurring  in  the  single  instance 
of  a  graphite  skin  exposed  for  five  days  to  a  temperature  of  248°  F., 
which  shortened  5  per  cent  and  lost  in  weight  9  per  cent. 

The  smallest  change  was  also  in  a  graphite  skin  exposed  for  five 
days  to  a  temperature  of  120°  F.,  that  shortened  1.2  per  cent  and 
lost  in  weight  4.4  per  cent,  and,  though  visibly  affected  in  elasticity, 


PAINT   TESTS.    SPENNRATH'S  EXPERIMENTS.  303 

was  changed  the  least  in  other  respects.  All  the  other  skins  became 
brittle  and  stiff,  broke  easily  when  bent  sharply,  and  were  darkened 
in  color.  The  white-lead  skin  changed  to  a  faint  yellow,  the  sul- 
phide of  lead  and  zinc  oxide  skin  to  an  intense  yellow. 

The  addition  to  the  linseed  oil  of  10  per  cent  of  either  the  oil  of 
turpentine  or  other  driers,  or  a  mineral  oil,  or  other  fatty  non-drying 
oils,  including  some  gum  copal,  had  no  effect  whatever  to  resist  the 
changes  effected  by  the  heat.  Not  more  than  10  per  cent  of  mineral 
oil  could  be  added  to  the  linseed  oil,  as  it  rendered  the  paint  viscous 
after  drying.  The  Bessemer  paint-skin,  the  pigment  being  a  ground 
furnace  slag,  and  the  linseed-oil  vehicle  having  an  addition  of  a  non- 
drying  fatty  oil  with  some  gum  copal,  was  just  as  sensitive  to  the 
heat  as  any  oil  paint. 

Generally  the  action  of  the  heat  was  less  marked  upon  the 
graphite  skins,  which  were  less  brittle  than  those  made  from  white 
lead  or  zinc-white.  The  red-lead  skins  were  especially  sensitive  to 
mechanical  influences. 

These  changes  are  easily  accounted  for.  The  oily,  repellent 
nature  of  the  flake  graphite  prevented  it  from  bonding  to  the  oil 
vehicle  as  firmly  as  the  other  natural  pigments  and  those  of  higher 
specific  gravity  will  do  in  both  a  green  or  a  thoroughly  dried  paint. 
While  it  is  generally  known  that  heat  is  destructive  to  oil-paint 
coatings,  it  does  not  follow  that  the  coatings  are  so  sensitive  to  its 
action  that  it  may  be  deemed  the  principal  cause  of  their  failure. 
The  engine  and  fire-rooms  of  ocean  steamers  and  war-vessels  are 
exposed  to  temperatures  of  120°  to  140°  F.  for  months  at  a  time, 
and  many  times  in  succession  in  atmospheres  heavily  charged  with 
moisture  and  other  vapor,  without  any  material  disturbance  to  the 
protective  character  of  the  coatings. 

There  are  commercial  paints  in  extensive  use,  subject  to  tem- 
peratures of  300°  to  350°  F.  under  pressures  of  steam,  which  preserve 
their  integrity  after  years  of  exposure.  In  these  instances  the  life 
of  the  coating  depends  quite  as  much  upon  the  vehicle  as  upon  the 
pigment. 


CHAPTER  XXXI. 

PAINTING   BY   SPRAY. 

PAINTING  by  spray  or  the  air-brush  has  lately  come  largely  into 
use;  in  fact,  it  would  have  been  impossible  to  have  covered,  in  any 
acceptable  manner,  the  World's  Fair  Buildings  erected  since  1890, 
without  the  use  of  the  paint-spray  process. 

At  the  Columbian  Exposition,  the  results  of  the  spray  method 
of  painting,  compared  with  the  use  of  the  hand-brush,  were:  A 
corps  of  hand-brush  painters,  working  in  the  usual  manner  of  apply- 
ing kalsomine,  averaged  about  800  square  feet  of  surface  daily,  while 
16,000  to  20,000  square  feet  were  covered  by  a  spray-machine  in 
eight  hours,  30,000  square  feet  having  been  reached  under  favorable 
conditions.  In  the  Manufacturers'  Building,  with  a  daily  average 
of  thirty  men  using  spray-machines,  at  the  end  of  eighteen  working 
days,  1,332,700  square  feet  of  surface  had  been  covered;  equal  to 
an  average  of  2368  square  feet  per  day  per  man.  This  was  during 
the  coldest  days  of  winter,  when  the  water  paint,  in  attempting  to 
spread  it  by  hand,  froze  solid.  The  spray  required  about  twenty-one 
gallons  of  kalsomine  against  twenty  gallons  by  the  brush,  but  the 
saving  in  labor  was  nearly  twenty  to  one  in  favor  of  the  spray  process. 

Gas-holders  in  duty  are  exceptionally  hard  to  paint.  One  painted 
by  spray,  using  iron-oxide  paint,  averaged  from  2700  to  2900  square 
feet  of  surface  per  hour  for  three  men  using  two  sprays.  The  amount 
of  paint  used  was  not  notably  more  than  with  the  brush.  The  cost 
of  the  labor  was  less  than  J  cent  per  square  yard. 

In  the  Michigan  Engineers'  Manual  for  1897,  Mr.  J.  J.  Huber 
describes  an  extemporized  spray-machine,  and  the  results  in  paint- 
ing 100,000  square  feet  of  rough  hemlock  siding  with  iron-oxide  and 
raw-oil  paint. 

The  contractor's  bid  for  labor,  ladders,  and  brushes, 

the  company  to  furnish  the  paint,  was 35  cents  per  100  square  feet 

The  company  to  furnish  all  the  material 28     "       "      "        "         " 

A  lump  bid  for  the  labor  alone 30     "       "      "        "         " 

304 


PAINTING  BY  SPRAY.  305 

The  mill  company  built  a  spray-machine  for  twenty  dollars,  and 
the  result  of  its  use  was,  that  one  gallon  of  paint  covered  150  square 
feet  of  rough-board  surface.  Two  men  covered  5000  square  feet 
per  day.  Cost  of  the  paint  applied,  ten  cents  per  100  square  feet. 
Cost  of  the  paint,  labor,  and  apparatus,  fifteen  cents  per  100  square 
feet,  or  less  than  one-half  that  of  painting  by  hand.  The  paint  could 


FIG.  41. — Field  spray  apparatus  at  work. 

be  applied  from  eight  to  ten  feet  above  the  spraymens'  heads,  and 
ordinary  laborers  could  do  the  work. 

In  some  experiments  made  by  the  P.  &  L.  E.  R.  R.,  using  a  spray 
apparatus  for  painting  box  freight-cars,  the  time  required  was  thirty 
minutes  per  car;  one  man  with  an  eight-inch  brush  following  the 
spray  thirty  minutes  more,  or  total  of  one  hour  per  car  for  each  coat. 
To  paint  a  60,000-pound-capacity  coal-car  required  two  men  twenty 
minutes  each,  spraying  the  lettering  not  included. 

At  the  Master  Car  and  Locomotive  Painters'  Association,  in  1897, 


306 


PAINTING  BY  SPRAY. 


Mr.   H.   G.   MacMasters,   M.C.P.I.C.RR.,   reported   the  comparative 
time  and  costs  in  detail  of  painting  box  freight-cars  by  brush  and  spray. 


With  the  Brush. 


With  the  Spray. 


Work  Coated. 
Sills,  one  coat  

Time. 
4             20  min. 

Cost. 
$0  05 

Time. 
13  min. 

Cost. 
$0.031 

Edge  board,  one  coat  

40    " 

0  10 

17    " 

0  041 

Body,  three  coats  

7  hrs. 

1.05 

84    " 

0.21 

Puttying  up  

1    " 

0.15 

1  hr. 

0.15 

Roof,  two  coats  

.             30  min. 

0  074 

12  min. 

0.03 

Trucks,  one  coat.     .    .    . 

£;            1  hr 

0  15 

20    " 

0  05 

Blacking  ironwork  

.              25  min. 

O.OGi 

25    " 

0.061 

Totals. 10  hrs.  55  min.      $1.63f    3  hrs.  51  min.        $0.57f 

Result  1.98  to  one  in  time,  and  2.82  in  cost,  in  favor  of  the  spray. 

The  danger  to  the  health  of  the  painters  in  the  use  of  the  spray 
is  very  marked  over  that  in  the  use  of  the  brush,  whether  kalsomine, 
iron  oxides,  or  mixed  paints  are  used.  In  the  spraying  of  lead  paints 
or  those  containing  any  metallic  oxides  the  dangerous  effects  are 
greatly  increased,  even  when  the  greatest  possible  care  is  used  to 
guard  against  them.  The  fine  mist-like  spray  is  readily  taken 
into  the  lungs  at  every  respiration,  and  is  more  thoroughly  intro- 
duced into  the  system  than  is  possible  by  absorption  from  contact  in 
painting  by  hand. 


FIG.  42. — Mathewson's  patent  helmet  for  painting  by  spray  or  cleaning  by 

the  sand-blast. 

The  extra  amount  of  paint,  about  5  per  cent,  used  by  the  spray 
is  offset  many  times  by  the  saving  in  labor,  as  above  noted. 


PAINTING  BY  SPRAY. 


307 


These  were  applications  from  compressed-air  installations  used 
for  other  purposes  than  painting. 

The  merit  of  oil-paint  spray  coatings  has  not  been  fully  estab- 
lished. The  spray  necessarily  carries  a  part  of  the  air  with  the  con- 
densed moisture  in  it  into  the  paint,  and  its  subsequent  escape  by 
expansion  and  evaporation  must  result  in  a  more  porous  coating 
than  with  paint  applied  by  a  hand-brush.  Following  the  spray 
immediately  with  a  brush  will  remove  the  porosity  to  some  extent. 
The  brushing  out  of  any  paint  is  a  great  factor  in  its  durability,  and 
as  the  use  of  the  spray  renders  the  employment  of  a  cheaper  grade 
of  labor  more  feasible  than  with  the  use  of  the  brush,  the  effects 
.of  an  indifferent  use  of  painter's  " elbow-grease"  will  soon  reveal  itself 
in  the  decay  of  the  coating. 


FIG.  43. — Barrel  and  hand-power  spray  apparatus. 

Upon  metallic  surfaces  the  sprayed  paint  proves  more  perish- 
able than  when  applied  to  wood. 

For  use  in  the  field  for  repainting  iron  bridges,  walls,  and  other 
structures  there  may  be  a  saving  in  time  of  the  painters,  scaffold- 
ing, etc.,  but  the  work  cannot  be  as  well  done  as  by  the  use  of  the 
brush.  The  cheaper  and  less  responsible  laborer  generally  em- 


308  PAINTING  BY  SPRAY. 

ployed  to  use  the  spray  apparatus  will  neglect  the  necessary  scrap- 
ing and  steel- wire  brushing  requisite  in  all  repainting  work,  as  well 
as  the  subsequent  brushing  out  of  the  spray  coating,  particularly 
in  the  places  difficult  of  access,  where  a  thorough  application  of 
the  paint  is  most  necessary.  Peeling  of  the  paint  and  corrosion 
promptly  follow  any  extended  application  of  an  oil-paint  spray 
coating  on  a  ferric  body  in  situ. 

The  methods  of  painting  were  recently  discussed  by  the  Western 
Association  of  Railway  Superintendents  of  Bridges  and  Buildings, 
in  answer  to  a  circular  asking  for  information  upon  the  subject. 
Eighteen  answers  were  received.  All  were  in  favor  of  the  sand- 
blast for  cleaning  either  new  or  old  metallic  surfaces  preparatory 
to  painting. 

Six  were  in  favor  of  the  air-spray  for  some  classes  of  work,  three 
were  opposed  to  it,  and  nine  were  non-committal.  Two  who  had 
tried  it  were  opposed  to  it.  One  superintendent  said:  "On  iron 
bridges  other  than  on  plate  girders  I  found  that  there  was  more 
paint  wasted  than  applied  to  the  structure.  The  waste  in  attempt- 
ing to  paint  lattice-truss  work  was  very  marked,  and  the  coating 
was  not  equally  or  well  spread."  He  favored  the  use  of  a  stiff  hard 
brush  to  insure  a  close  contact  of  the  paint,  which  he  could  not 
get  with  the  spray.  Too  much  air  was  incorporated  with  the 
paint  by  the  spray,  and  would  not  release  tself  in  the  drying  of  the 
paint.  It  left  the  coating  more  porous  than  with  the  use  of  hand- 
brushes.  Following  the  spray  with  a  hand-brush  did  not  materially 
help  the  coating  in  durability,  when  compared  with  surfaces  spread 
on  the  same  structure  at  the  same  time,  by  the  same  painters  using 
hand-brushes,  and  the  same  paint. 

"The  use  of  the  spray,  following  it  with  a  heavy  hand-brush, 
was  admissible  upon  some  of  the  large  wooden  buildings,  as  the 
failure  of  the  paint  in  these  cases  was  not 
attended  by  corrosion,  blistering  being  the 
principal  cause  of  failure  in  the  sprayed  coat- 
ing on  wooden  and  masonry  surfaces." 

Generally,  heavy  or  very  thick  oil  paints 
cannot    be    successfully    spread    by    spray, 

Fi    44 Hand  soray     unless  under  air  pressures  of  sixty  or  more 

apparatus.  pounds   per  square  inch.      This  renders  the 

use  of  the  spray  for  oil  paint  useless,  unless  power  other  than  hand- 
power  is  available,  or  the  paint  is  applied  quite  hot  to  increase  its 


PAINTING  BY  8  PR  AY  309 

fluidity.  If  the  paint  is  thinned  with  benzine  or  turpentine  to  the 
point  where  a  moderate  pressure  of  air  will  enable  the  spray  to 
work  without  choking  in  the  nozzle,  all  of  the  objections  to  this  class 
of  paints  are  increased,  as  the  extra  amount  of  volatiles  in  them  to 
be  evaporated  leaves  the  coating  more  porous  and  hastens  its  decay. 
Two  coats  of  such  air-sprayed  paints  are  required  to  equal  in  pro- 
tecting power  one  coat  of  heavy  hand-brush  work. 

With  kalsomining  or  water  paints  the  spray  apparatus  finds  an 
almost  uncontested  field,  and  from  the  great  saving  in  labor  is  recom- 
mended. 


CHAPTER  XXXII. 

MIXED    PAINTS. 

REPUTABLE  manufacturers  of  standard  pigments  are  greatly 
at  the  mercy  of  many  of  the  proprietary  or  patent  paints  ready 
for  use  that  are  a  feature  of  the  paint  market. 

Standard  pigments  subsequently  appear  in  these  compound  paints 
mixed  with  a  variety  of  well-known  inferior  substances  that  by 
some  alleged  special  mechanical  manipulation  "  developed  in  our  fac- 
tory" makes  of  them  a  preeminently  superior  product,  "wholly 
unlike  that  produced  by  the  antiquated  process  employed  before  the 
advent  of  our  new  idea." 

Mixed  paints  for  the  great  bulk  of  the  paint  trade  are  a  con- 
venience that  cannot  be  ignored,  and  are  in  conformity  with  the 
general  advancement  of  the  times.  Responsible  manufacturers 
and  dealers  in  paints  furnish  them;  and  they  are  more  uniform  in 
quality  and  color,  of  better  composition,  as  well  as  cheaper,  than  when 
mixed  by  the  individual  painter. 

Responsible  paint  manufacturers  inspect  and  test  the  quality 
of  all  their  materials,  and  are  certain  that  they  are  standard  in  all 
respects,  more  than  it  is  possible  for  the  individual  painter  to  do, 
however  much  he  may  desire  to  produce  a  good  paint. 

Railway  companies  and  bridge-manufacturing  firms,  from  the 
magnitude  of  their  painted  work,  are  able  to  employ  the  necessary 
staff  to  secure  good  materials,  also  the  technical  knowledge  to  mix 
and  apply  them.  The  application  of  the  paint  in  a  great  measure  is 
under  their  control,  and  the  composition  of  it  can  be  varied  to  meet 
all  the  conditions  as  they  arise,  and  a  direct  responsibility  established 
for  any  failure  in  the  coating. 

Failures  are  possible  and  occur  with  the  best  of  paints.  The 
hardest  to  locate  and  most  annoying  is  where  the  painter,  unmindful 
of  the  atmospheric  conditions  or  the  state  of  the  surface  he  is  at  work 

310 


MIXED  PAINTS. 


311 


upon,  finding  that  the  paint  does  not  work  or  spread  well,  doses  it 
with  benzine,  turps,  or  some  other  volatile  or  vehicle.  He  does  not 
always  know  or  care  what  the  composition  of  either  the  paint  or  the 
added  element  is,  so  that  it  enables  him  to  get  through  with  his  work 
without  an  immediate  appearance  of  distress  in  the  coating. 

Special   mixed    commercial    paints   generally   require   a   special 
order  of  procedure  in  their  application,  and  when  these  are  faithfully 


FIG.  45. — Power  paint-mixer. 

carried  out  will  usually  give  better  results  than  when  the  applica- 
tion is  left  to  the  ordinary  painter's  manipulation. 

A  few  special  paints  that  have  passed  the  fortuitous  require- 
ments of  the  United  States  and  foreign  patent  offices,  and  have 
one  or  more  trade-marks  to  each  combination,  are  the  following: 

Fire-  and  water-proof.  Composition:  coal-tar,  oil,  gypsum,  Japan, 
liquid  rubber,  nitric  acid,  slate-dust,  sal-soda,  potash,  antimony, 
and  sodium. 

Another  combination  of  coal-tar,  yellow  ochre,  plumbago,  lime, 
salt,  and  coal-oil. 


312  MIXED  PAINTS. 

Fire  and  acid-proof.  Composed  of  coal-tar,  pitch,  common 
mineral  paint,  hydraulic  cement,  gray  ochre,  asbestos,  slaked  lime, 
liquid  drier,  and  litharge. 

In  most  of  the  above  and  in  other  similar  patent  compounds 
the  quantities  of  each  substance  are  not  defined,  but  left  to  the  dis- 
cretion of  the  user. 

Other  compounds  of  a  kindred  nature  contain  saltpeter,  sulphur, 
caustic  potash,  mica,  talc,  zinc  slag,  salts  of  tartar,  oxide  of  copper, 
shellac,  sulphate  of  mercury  and  sulphate  of  zinc,  verdigris,  copperas, 
india-rubber,  hydraulic-cement  slag,  soapstone,  solutions  of  gall- 
nuts,  tannin,  acetone,  yellow  soap,  lignum  vitse,  garlic,  asafetida, 
and  one  or  more  of  the  list  of  inert  pigments  given  in  Chapter 
XVIII. 

These  compounds  are  recommended  as  special  paints  for  ferric 
structures.  In  most  cases  the  merits  are  so  blindly  set  forth  that 
one  is  in  doubt  whether  it  is  the  preservation  or  destruction  of  the 
paint  or  the  covered  surface  the  proprietor  wishes  to  secure. 

As  mentioned  before,  all  mixed  paints  are  not  necessarily  objec- 
tionable compounds,  and  to  be  avoided.  A  combination  of  pigments 
to  secure  a  desired  result  is  often  necessary  where  the  use  of  one 
pigment  would  be  ineffective. 

In  the  cases  of  red  lead  and  lampblack  the  lampblack  delays  the 
setting,  adds  body,  prevents  the  crawl  or  curdling  of  straight  red- 
lead  coatings,  and  is  in  every  way  beneficial  to  the  physical  charac- 
ter of  the  paint. 

There  is  enough  oxidizing  element  in  the  red  lead  to  cause  the 
lampblack  (which  is  a  slow  drier)  to  dry  without  using  a  large 
amount  of  japan  or  other  drier. 

A  small  amount  of  French  ochre  is  sometimes  added  to  red- 
lead  and  lampblack  mixtures  to  give  a  brighter  tone  to  the  choco- 
late color  of  the  mixture,  making  what  is  called  the  "Pullman  color." 
This  mixture  has  proved  to  be  very  reliable  under  some  severe 
exposures  on  cars. 

The  specifications  for  the  painting  of  one  of  the  largest  bridges 
in  the  world  called  for  a  pure  red-lead  paint.  Analysis  of  the  paint 
after  the  bridge  was  painted  showed  that  the  paint  contained  2 
pounds  of  whiting  and  aniline  color  to  1  pound  of  red  lead.  This 
paint  was  completely  disintegrated  and  ruined  after  only  one  year's 
exposure. 

A  mixture  of  70  per  cent  of  barytes  and  10  per  cent  each  of  car- 


MIXED  PAINTS.  313 

bon  black,  zinc  oxide,  and  amorphous  graphite,  well  ground  together 
in  linseed-oil  containing  a  small  amount  of  Japan  drier,  will  outwear 
red  lead.  If  the  coating  is  applied  to  a  rusty  surface,  the  scales  of 
rust  will  break  through  red  lead  sooner  than  through  the  above 
mixture. 

Mixtures  of  zinc-white  and  white  lead,  both  true  pigments,  are 
thought  by  some  engineers  to  be  a  more  durable  coating  than  either 
alone,  and  for  some  external  exposures  are  said  to  be  improved  by 
the  addition  of  10  to  15  per  cent  of  silica  or  barytes. 

The  barytes  and  silica  in  these  cases,  also  when  added  to  flake 
graphite,  save  oil  and  give  weight  and  bulk,  as  well  as  a  frictional 
element  to  hold  the  graphite  in  place  during  the  setting  of  the 
paint. 

In  all  these  instances  the  paint  appears  to  be  better  for  the  pres- 
ence of  the  various  substances;  but  could  the  same  group  of  mate- 
rials be  combined  into  a  single  pigment,  it  would  prove  superior  to 
any  mechanically  arranged  article. 

The  few  cases  where  the  mixture  of  true  pigments  with  each  other 
or  with  an  inert  substance  has  proved  to  be  beneficial  are  not 
numerous  enough  to  afford  any  foundation  for  a  mass  of  incongru- 
ous substances  called  " mixed  paints"  that  flood  the  market,  and 
which  the  reputable  paint-manufacturer  is  almost  powerless  to  stem. 
(See  Chapters  V-XXX.) 

No  reliable  paint  can  be  made  without  skilled  labor  at  almost 
every  stage  of  its  manufacture,  even  with  the  aid  of  the  best  me- 
chanical devices  to  reduce  the  labor  account.  Generally  the  labor 
and  power  account  is  two  and  a  half  to  three  cents  per  pound  of 
paint,  or  twenty-five  to  thirty  cents  per  gallon.  Any  paint  worth 
applying  to  a  ferric  or  any  other  structure  of  importance  cannot 
be  bought  for  forty  or  fifty  cents  a  gallon.  Such  paint  will  not  pro- 
tect a  ferric  body,  and  if  applied  will  prove  (because  of  frequent 
renewals)  more  expensive  than  one  costing  three  times  as  much. 

Iron  oxide  is  the  cheapest  straight  pigment  in  use.  But  this 
cannot  be  properly  ground  in  a  reliable  oil,  barreled,  and  delivered 
for  less  than  seventy  cents  per  gallon,  unless  the  manufacturer  is 
losing  money,  or  using  an  adulterated  oil  or  a  very  unreliable  iron- 
oxide  pigment. 

Mixed  paints  containing  resin,  resin-oil,  coal-tar  in  any  form, 
calcium  chloride  or  sulphate,  and  iron  oxide  act  as  carriers  of 
oxygen  and  promote  corrosion;  hence  they  are  unreliable  coatings. 


314  MIXED  PAINTS. 

The  quality  of  the  linseed-oil  used  in  many  of  the  mixed  paints  is 
against  them.  Oil  made  from  unripe,  smoky,  condemned,  or  "no- 
grade"  seeds,  that  often  contain  almost  as  much  non-drying  oil  as 
the  drying  element,  is  too  frequently  used,  and  benzine  is  used  for 
.ihe  drier  instead  of  japan  or  turpentine.  When  linseed-oil  is  heated 
to  120°  or  130°  Fahr.,  and  benzine  is  slowly  added  and  well  stirred, 
the  mixture  will  not  separate  on  cooling,  but  remain  fixed  until  the 
oil  is  spread  and  dried  by  the  evaporation  of  the  volatile.  The  odor 
of  the  benzine  in  the  paint  in  this  case  is  almost  suppressed;  it  is 
only  markedly  noticeable  when  the  oil  is  again  heated  to  near  the 
above  degree. 

Hot  mineral  oil  added  to  linseed-oil  is  hard  to  detect  by  the  odorr 
but  the  character  of  the  mineral  oil  as  a  non-drying  oil  is  not  changed 
in  the  slightest  degree  by  the  heating.  A  gill  of  mineral  oil  added 
to  a  gallon  of  red-lead  paint  will  delay  the  setting  of  the  paint.  The 
paint  never  dries  hard,  but  only  on  the  surface.  It  remains  viscid 
beneath,  and  the  coating  is  liable  to  peel  at  any  time. 

There  were  sold  in  the  United  States  in  the  year  1900  60,000,000 
gallons  of  mixed  paints  and  pastes,  the  use  of  which  is  increasing 
about  10  per  cent  each  year.  More  paint  is  used  in  the  United 
States  per  capita  than  in  any  other  country.  The  English  mixed 
paints  are  adulterated  quite  as  much  as  any  paints  produced  in 
the  United  States. 

The  highly  extolled  English  "Torbay"  paint  is  made  from  a  90 
per  cent  iron-oxide  pigment,  and  has  no  merit  over  any  American 
brand  of  oxide  paint  containing  the  same  percentage  of  iron  oxide 
and  an  equal  quality  of  American  linseed-oil. 

"Ferredor,"  an  English  trade-mark  mixed  paint,  is  exploited 
as  being  manufactured  from  a  "natural  metallic  steel-gray,  95  per 
cent  rustless  peroxide  of  iron  found,  in  a  very  fine  state  of  division, 
as  a  crystalline  peroxide,  and  surpasses  the  oxides  of  iron,  and  is 
superior  to  red  lead.  ' Ferredor '  cannot  absorb  or  impart  oxygen, 
so  that  the  oil  in  the  paint  is  not  destroyed,  as  is  the  case  with  the 
red  oxides,"  etc. 

The  most  brazen  advertiser  of  any  grade  of  American  mineral 
brown  paint  never  equalled  this,  and  no  American,  has  been  bold 
enough  to  attach  to  his  product  so  fearful  a  trade-mark  as  "Schuppen- 
panzerfarbe." 

Crosbie's  paint  (English)  is  honestly  stated  as  being  made  from  a 
90  per  cent  oxide  of  iron,  unadulterated  and  extra-fmely  ground 


MIXED  PAINTS.  315 

in  the  best  linseed-oil.  Five  governments  and  one  hundred  and 
thirty  corporations  show  their  confidence  in  an  honestly  made  paint 
by  using  this  firm's  product,  though  it  is  but  a  corrosive  one. 

"Armour-Scale  Paint"  (Panzerschuppen).  A  Swiss  ferric  paint 
made  from  a  number  of  formulae,  also  one  or  more  German  paints 
bearing  the  same  trade-mark,  are  simply  iron-oxide  paints  made 
from  80  to  90  per  cent  iron  ores  that  the  manufacturers  call  "granular 
micaceous."  A  greasy,  crystalline,  scaly  iron  ore  with  gangue,  etc. 
Graphite  in  some  (unclassified)  form  is  added  and  the  vehicle  is  some- 
times a  linseed-oil  varnish. 

"Lender's  Anti-Corrosive  Paint,"  especially  recommended  as 
impervious  to  heat,  cold,  warm  water,  steam,  volatile  acids,  alkalies, 
gaseous  ammonia,  hydrochloric  acid  gas,  and  sulphuretted  hydrogen 
gas.  The  base  of  the  pigment  is  called  "a  silicate  of  iron."  It  is 
simply  an  ordinary  iron  ore  containing  iron-oxide,  88.56  per  cent; 
silica,  5.40  per  cent;  lime  and  magnesia,  3.10  per  cent;  alum  and 
phosphoric  acid,  0.55  per  cent;  undetermined  substances  and  loss, 
4.39  per  cent.  It  is  sold  in  the  form  of  a  paste,  being  finely  ground 
in  a  boiled  oil  or  varnish,  and  when  used  is  reduced  with  raw  linseed- 
oil,  and  litharge  added  for  a  drier.  A  special  point  claimed  for  this 
wonderful  oxide-of-iron  paint  is  that  "any  mineral  paint  of  the 
right  color  can  be  added  to  produce  the  desired  tone."  Won- 
derful product!  The  special  advantages  for  this  special  paint  are 
accompanied  by  a  specially  high  price  for  it. 

Other  examples  of  the  foreign  mixed  paints  and  the  art  of  adver- 
tising them  could  be  cited.  A  mixed  paint  is  not  necessarily  a  good 
one  because  of  its  trade-mark  and  high  price,  nor  is  it  a  notoriously 
bad  one  because  of  its  being  an  American  firm's  product. 

Some  instances  of  the  unreliable  character  of  compound  paints 
have  been  given  in  Chapters  V  (White  lead)  and  XXX  (Paint 
tests).  The  following  instance,  from  the  cost  and  magnitude  of  the 
structure  to  which  the  paint  was  applied,  the  public  interests  at 
stake,  and  the  result  of  the  application,  is  of  interest.  It  illustrates 
the  unreliable  character  of  compounded  pigments  applied  over 
other  basic  pigment  paints  for  the  protection  of  ferric  struc- 
tures. 

The  new  suspension  bridge  over  the  East  River  has  in  Brooklyn 
a  viaduct  about  9000  feet  long.  This  viaduct  is  of  lattice  trusses 
and  columns  of  the  type  used  for  elevated  railways. 

The  steel  for  this  structure  was  specified  and  supposed  to  have 


316  MIXED  PAINTS.     BROOKLYN  BRIDGE   VIADUCT. 

been  cleaned  by  the  sand-blast,  but  it  mostly  received  only  a  coating 
of  boiled  oil  before  machining.  After  riveting  up  in  sections  pre- 
paratory to  shipment  it  received  a  coating  of  red-lead  paint,  and 
after  erection  another  coating  of  red  lead  and  lampblack  paint  was 
applied. 

After  a  number  of  months'  drying  the  first  finishing  coat  of  Jewett's 
white  lead,  70  to  75  parts,  and  the  New  Jersey  zinc  oxide,  20  to  25 
parts,  ground  in  raw  linseed-oil,  was  applied.  The  engineer  corps, 
from  some  previous  experience  with  this  mixture,  were  particular 
to  see  that  the  quality  of  all  the  materials  was  standard  in  all  respects. 
The  spreading  of  this  and  the  following  or  fourth  coat  was  in  situ 
and  under  their  eyes;  hence  they  alone  are  to  blame  for  any  errors 
in  this.  After  a  number  of  months,  the  fifth  or  finishing  coat,  com- 
posed of  the  above  white  lead  and  zinc  oxide  mixture,  also  a  small 
quantity  of  French  ochre  to  make  the  coat  cream-colored,  was  ap- 
plied. 

In  a  not  particularly  severe  exposure,  and  in  two  years,  the  last 
three  lead  and  zinc  coatings  were  disintegrated  and  washed  away 
in  large  areas  over  the  entire  structure,  showing  the  foundation 
coats  of  red  lead.  A  cloth  wetted  in  water  and  wiped  over  the  coat- 
ings washed  them  off  as  freely  as  though  they  were  of  whitewash. 
Wringing  the  cloth  left  the  three  coats  of  lead  and  zinc  pigments  in 
the  water  like  so  much  chalk.  If  the  percentage  of  zinc  oxide  in 
the  coating  had  been  forty,  the  paint  would  have  failed  by  peeling 
in  strips  instead  of  chalking.  The  paint,  in  its  materials,  propor- 
tions, application,  location,  and  exposure,  is  not  far  different  from 
that  of  the  New  York  City  elevated  railways,  which  thus  far  has 
kept  its  place  free  from  chalking,  but  has  not  prevented  corrosion 
from  attacking  every  foot  of  the  structure  beyond  the  possibility  of 
correction. 

Had  the  same  amount  and  quality  of  the  paint  been  spread  on 
a  thousand  inland  structures,  the  failure  of  the  coatings  would  not 
have  been  so  marked  as  in  the  above  case,  where  the  agency  of  acres 
of  decayed  paint  tells  the  tale;  but  it  would  have  occurred  just  the 
same,  though  the  loss  would  have  been  so  widely  distributed  as  to 
call  no  special  attention  to  it. 

The  reliable  qualities  of  a  paint  composed  of  a  number  of 
pigments,  or  a  compound  paint,  where  the  substances  of  the  com- 
pound are  united  as  an  individual  whole  by  chemical  affiliation 
in  the  process  of  manufacture,  have  been  mentioned  a  number  of 


MIXED  PAINTS 


317 


times  in  this  work.     The  annexed  figure  (46)  illustrates  the  dura- 
ble nature  of  that  class   of  pig-    

ments. 

It  is  the  photograph  of  a 
four-inch-diameter  wrought-iron 
pipe.  The  upper  end,  A,  was  en- 
closed unpainted  in  a  cast-iron 
ring.  The  lower  end,  B,  is  the 
adjoining  part  of  the  pipe  that 
had  been  painted  with  two  coats 
of  sublimed  lead  and  zinc.  The 
pipe  and  its  connections  were 
buried  in  the  earth  for  nine  years. 
When  taken  up  the  end  A  had 
corroded  and  lost  over  -fa  inch 
in  diameter.  The  part  B  was 
uncorroded  and  nearly  all  of 
the  paint  on  the  whole  length 
of  pipe  was  unchanged  and  in 
place.  Where  the  coating  was 
scaled  off  in  the  process  of  re-  FlG  46._Four-inch  wrought-iron  pipe, 
moving  the  pipe  from  the  trench, 

the  iron  was  as  clean  and  uncorroded  as  when  laid.     (See  Chapter 
V,  Sublimed  Lead.) 

Sir  Benjamin  Baker  has  concisely  remarked  that  "it  is  the 
deviation  from  the  average  which  really  is  so  important  in  the  design 
of  engineering  works." 

This  is  equally  applicable  to  the  design  of  a  paint.  The  majority 
of  paint-manufacturers  appear  to  harbor  the  idea  of  the  universal- 
ity of  their  product.  They  give  little  or  no  attention  to  location, 
exposure,  or  the  many  influences  to  which  it  may  be  subjected  during 
its  life  on  a  ferric  structure. 

A  paint  that  is  reliable  in  open  inland  locations  often  fails  on 
the  seacoast,  or  in  manufacturing  towns,  or  on  industrial  establish- 
ments. The  paint  that  is  reliable  in  the  latter  place  may  fail  quickly 
on  another  not  far  distant  location  because  of  disregarding  one  or 
more  of  the  above  factors. 

It  is  important  that  both  the  engineer  and  the  paint-compounder 
remember  that  there  are  a  number  of  affinities  in  a  paint  coating. 
These  are  where  the  vehicle  and  the  pigments  are  capable  of  mixing, 


318  ENAMEL  PAINTS. 

not  to  form  a  new  chemical  compound,  but  to  influence  the  action  of 
one  of  the  group;  for  instance,  where  red  lead  or  red  lead  and 
lampblack  are  added  to  influence  the  drying  of  the  paint.  Another 
instance  is  where  a  substance  combines  in  definite  proportions,  such 
as  the  carbonate  of  lime  added  to  an  iron  oxide  to  neutralize  the 
sulphur  in  the  pigment,  or  the  acid  in  the  vehicle. 

It  is  also  to  be  kept  in  mind  that  every  metal  is  electropositive 
to  its  own  oxide;  the  latter  induces  corrosion  in  the  former  when- 
ever the  two  are  brought  into  contact,  as  in  a  paint  coating.  The 
vehicle  only  insulates  or  protects  either  substance  but  indifferently, 
particularly  where  the  covered  metal  is  the  base  of  the  oxide  in  the 
paint.  The  water  and  acids  in  the  oil  (the  latter  not  infrequently 
rancid)  have  great  influence  in  the  decay  of  the  coating  and  corrosion 
of  the  covered  metal. 

The  production  of  enamel  paints  has  become  a  trade  of  great 
importance.  They  differ  from  ordinary  oil-vehicle  paints  inasmuch 
as  they  dry  with  a  high  lustre  or  gloss.  They  were  first  called  "var- 
nish paints/'  for  the  reason  that  the  vehicle  was  a  varnish,  instead 
of  linseed-oil.  They  are  used  principally  for  coating  walls  on  the 
inside  of  buildings  that  require  to  be  washed  with  water,  as  in  hos- 
pitals, courtyards,  etc.,  the  varnish  vehicle  being  less  easily  injured 
by  the  water  than  an  oil  vehicle. 

The  use  of  a  varnish  vehicle  for  ferric  paints  has  been  tried  in  a 
number  of  instances  in  late  years  with  varying  degrees  of  success. 
The  principal  difficulty  in  their  use  is  the  uncertain  character  of  the 
varnish  vehicle,  which  requires  a  greater  knowledge  of  the  nature 
of  the  fossil  resins  and  how  to  compound  them  than  the  average 
paint-manufacturer  has  at  his  command. 

There  are  three  classes  of  enamels :  * 

First.  The  slow-drying  enamels,  that  require  from  twelve  to 
fifteen  hours  to  dry  under  normal  conditions.  They  give  a  fine, 
lustrous,  level  coating,  and  if  carefully  applied  should  show  no  brush- 
marks.  They  are  essentially  an  oil  and  fossil-resin  varnish,  with 
which  the  necessary  color  pigments  are  ground. 

Second.  Quick-drying  enamels,  that  dry  in  from  twenty  to  forty 
minutes  according  to  their  composition.  They  are  essentially  spirit 
varnishes,  colored  with  pigments.  They  leave  a  lustreless  or  flat 

*"  Enamel  Paints  and  how  to  use  them."  By  Geo.  W.  Hurst,  F.C.S. 
Western  Paint  Magazine,  Feb.  1900,  pp.  46,  47 


ENAMEL  PAINTS.  319 

surface,  are  apt  to  show  brush-marks,  and  are  not  as  durable  as  the 
slow-drying  enamels. 

Third.  Baking  enamels.  They  are  varnish  compounds  that  when 
heated  flow  into  a  uniform  and  lustrous  coating.  The  pigments 
added  to  them  give  them  body  and  color.  Sewing-machine  and 
bicycle  frames,  hardware,  etc.,  are  examples  of  these  coatings.  In 
larger  ferric  bodies  they  are  represented  by  the  baked  japans  ap- 
plied to  water-pipes.  (See  Chapter  XI.) 

The  composition  of  the  varnish  base  of  all  of  these  enamels  is 
the  essential  part,  and  in  most  cases  better  results  can  be  attained 
if  the  varnish  is  obtained  from  a  reliable  varnish-manufacturer  than 
where  the  painter  makes  it  himself.  Even  the  best  of  varnish- 
makers  fail  sometimes  to  produce  a  reliable  varnish  owing  to  many 
causes,  principally  from  the  use  of  common  resin  and  other  poor- 
quality  gums,  the  effect  of  which  is  the  "  crazing  "  of  the  coating. 

The  general  nature  of  the  varnish  base  is  indicated  in  the  follow- 
ing recipes  that  have  given  good  results : 

Sixty  pounds  of  good,  white  Sierra  Leone  copal,  mixed  with  10 
gallons  of  the  best  quality  of  hot  boiled  linseed-oil.  When  well 
cooked  add  16  gallons  of  turpentine  and  J  pound  of  linoleate  of 
manganese  for  a  drier.  This  varnish,  suitable  for  all  colors  from 
black  to  white,  should  be  ground  in  as  for  oil  paints. 

A  cheaper  grade  of  varnish  can  be  made  from  35  pounds  of  Kauri 
gum  and  15  pounds  of  Sierra  Leone  copal,  mixed  with  7  gallons  of 
hot  boiled  linseed-oil  and  1^  gallons  of  turpentine.  When  nearly 
cold,  thin  down  by  adding  10  gallons  of  turpentine.  This  will  be 
too  dark  for  white  enamels,  but  answers  for  all  other  colors. 

The  white  enamels  are  usually  made  by  adding  zinc-white  or 
lithopone  to  the  varnish.  They  work  well.  About  6  pounds  of  the 
white  is  required  to  a  gallon  of  the  varnish.  Whiting  and  pipe-clay 
are  detrimental;  they  make  the  coating  gray,  are  deficient  in  body, 
and  are  liable  to  cause  "  peeling." 

Black  enamels  require  4  pounds  of  lampblack  to  about  6  gal- 
lons of  either  grade  of  the  above  varnishes. 

A  quick-drying  varnish  base  is  made  from  Sandarac  gum,  10 
pounds;  soft  Manila  copal,  5  pounds;  gum  benzoin,  1  pound; 
methylated  spirit,  8  gallons;  or  4  gallons  each  of  methylated  spirit 
and  wood-naphtha.  This  varnish  is  suitable  for  all  colors  from  white 
to  black.  A  cheaper  varnish,  suitable  for  dark  colors  and  black,  is: 
Sandarac,  12  pounds;  shellac,  10 pounds;  benzoin,  2  pounds;  methyl- 


320  ENAMEL  PAINTS. 

ated  spirit,  12  gallons.  These  varnishes  dry  quickly.  A  slower- 
drying  varnish  is  made  from  gum  dammar,  14  pounds,  and  3  gallons 
of  turpentine. 

For  a  white  enamel  from  either  of  these  varnishes  grind  in  10 
pounds  of  zinc-white  or  lithopone  to  1  gallon  of  varnish. 

For  a  black  enamel  grind  in  5  pounds  of  zinc-white,  2  pounds  of 
carbon  black,  and  3  ounces  of  brilliant  ebony  spirit-black  to  1  gallon 
of  varnish. 

The  baking  enamels  are  not  essentially  different  from  the  first 
class  of  varnishes  herein  mentioned,  other  than  that  they  contain 
more  gum  or  resin  of  some  quality. 

A  few  special  recipes  are  the  following:  Best  grade  of  refined 
asphaltum,  70  pounds,  mixed  with  9  gallons  of  hot  linseed-oil  and  5 
gallons  of  gold  size.  Boil  until  ropy,  then  add  9  gallons  of  turpen- 
tine. This  is  for  a  black  coating. 

The  colored  enamels  require  a  better  grade  of  varnish  base,  which 
is  made  thus:  A  good  quality  of  Kauri  and  copal  gums,  each  20 
pounds;  animi,  5  pounds;  melt  together  and  mix  with  14  gallons  of 
hot  linseed-oil;  boil  until  stringy,  thin  with  18  gallons  of  turpentine, 
and  use  with  any  pigments  to  get  the  desired  color. 

A  quick-drying  black  enamel  is  composed  of: 

D.  C.  shellac 60        pounds 

Gum  sandarac 20 

Gum  benzoin 2 

Lampblack 5  " 

Castor-oil 0.75       " 

Spirit  aniline  black 1 . 50        " 

Methylated  spirit 25  gallons 

Wood-spirit 2 

Total 89 . 25  pounds  27  gallons 

The  pigments  assembled  with  all  of  the  above  varnishes  should 
be  of  the  best  quality,  particularly  the  lampblack.  Pulverized 
bituminous  coal  and  nearly  all  of  the  so-called  "carbon  blacks" 
prove  detrimental  to  the  quality  and  color  of  the  enamel.  No  ben- 
zine or  turpentine  can  be  added  to  any  of  the  above  varnishes  after 
they  have  left  the  cooking-kettle  without  affecting  the  gloss  of  the 
enamel. 

The  above  enamel  compounds  represent  only  a  few  that  are  put 
upon  the  market  under  many  special  names.  As  a  rule,  the  pro- 


ENAMEL  PAINTS.  321 

tective  value  of  all  enamel  paints  is  quite  as  variable  as  the  ordinary 
oil- vehicle  paints.  A  varnish  vehicle  does  not  always  secure  a  reliable 
ferric  coating,  unless  more  care  is  exercised  in  preparing  the  surface 
to  receive  it,  or  in  its  application,  than  the  average  painter  generally 
gives  to  these  matters.  The  use  of  resin  or  resin-oils  ii>  enamel  paints- 
is  as  disastrous  as  when  used  in  an  oil  paint. 


CHAPTER  XXXIII. 

CORROSION  OF  IRON  AND  STEEL. 

THE  difference  in  the  rate  of  corrosion  between  iron  and  steel 
as  given  by  different  authorities  varies  greatly.  The  reason  for 
this  is  plain :  the  conditions  of  each  reported  rate  of  corrosion,  whether 
the  result  of  laboratory  or  other  tests,  such  as  exposure  to  weather 
or  other  corroding  influences,  not  being  similar  in  all  respects,  are 
therefore  comparable  only  in  a  general  way. 

Pieces  of  iron  and  steel,  both  suitable  for  boiler-tubes,  were  made 
clean  and  bright,  then  placed  in  sandy  loam  with  which  had  been 
thoroughly  mixed  some  sodium  carbonate,  sodium  nitrate,  ammo- 
nium and  magnesium  chlorides.  The  earth  so  prepared  was  kept 
moist.  At  the  end  of  twenty-three  days  the  plates  were  taken  out, 
cleaned  and  weighed.  The  following  was  the  result: 

Iron  had  "ost  by  corrosion 0.84  per  cent. 

Steel    "      "     "         "        ... 0.72    "       " 

The  pieces  were  replaced  in  the  earth  and  left  for  twenty-eight 
days  longer,  or  sixty-one  days  in  all.  The  result  was: 

Iron  total  loss  by  corrosion 2.06  per  cent. 

Steel    "       "     "         "        1.79     "      " 

This  is  a  rate  of  corrosion  that  would  probably  have  caused  the 
disappearance  of  the  plates  inside  of  eight  years. 

Experiments  conducted  by  the  Admiralty,  Board-  of  Trade,  and 
Lloyds  prove  that  steel  corrodes  much  more  rapidly  than  iron 
when  exposed  to  the  action  of  salt  water;  also  that  the  commoner 
brands  of  iron  corrode  less  rapidly  than  the  better  brands  when 
exposed  to  the  same  influences.  With  steel  and  iron  both  unpro- 
tected and  exposed  to  the  same  action  of  the  weather  and  sea-water 
corrosion  advanced  at  the  rate  of  one  inch  in  depth  in  82  years 
for  the  steel  and  190  years  for  the  iron.  When  always  immersed  in 
sea-water  the  periods  are  one  inch  in  130  years  for  the  steel  and  310 
years  for  the  iron.  When  always  immersed  in  fresh  water  the 
periods  became  600  yea:s  for  the  steel  and  700  years  for  the  iron. 

322 


CORROSION  OF  IRON  AND  STEEL.  323 

Mr.  B.  H.  Thwait,  A.M.I. C.E.,  reports  that  a  bar  of  wrought  iron 
unprotected,  exposed  to  the  action  of  the  atmosphere  in  a  manu- 
facturing town,  demonstrated  that  a  bar  of  common  iron  one  inch 
by  four  inches  would  be  entirely  corroded  away  in  a  little  over  100 
years. 

Mr.  G.  Rennie's  experiments  in  1836  were  with  cubes  of  wrought 
iron,  cast  iron,  and  bronze  for  lighthouse  purposes.  The  cubes  in 
separate  vessels  were  immersed  for  seventy  hours  in  saline  solutions- 
considerably  stronger  than  sea-water.  The  cast  iron  lost  3  ^  of  its 
weight;  the  wrought  iron  ^f\o>  being  in  the  proportions  of  two  to 
one  in  favor  of  cast  iron.  The  bronze  lost  ^  oi>  or  °^  ^s  weigh^  a  result 
in  favor  of  bronze  over  cast  iron  of  three  to  one.  The  cast-  and 
wrought-iron  cubes  were  then  placed  in  a  strong  solution  of  one  part 
of  muriatic  acid  in  twenty-five  parts  of  Thames  water,  and  exposed 
for  twenty-one  hours.  The  cast-iron  cube  lost  -fa  of  its  weight,  the 
wrought-iron  only  ¥|¥,  being  eight  to  one  in  favor  of  the  wrought 
iron. 

In  these  experiments  with  the  same  samples  of  each  metal  the 
results  were  directly  contrary.  The  crystalline  nature  of  the  cast 
iron  evidently  favored  the  disruption  of  the  crystals  from  their  bond 
or  loose  association  together;  they  were  cast  off  when  partially  cor- 
roded, and  corroded  by  themselves  while  the  acid  had  fresh  sur- 
faces to  act  upon  in  all  directions. 

The  experiments  of  Mr.  Robert  Mallett,  M.I.C.E.,  on  wrought 
iron  and  cast  iron  sunk  in  the  sea,  showed  that  from  -fa  to  j4^  inch 
in  castings  one  inch  thick,  and  about  T6F  inch  of  wrought  iron,  will 
be  destroyed  in  a  century  in  clear  sea-water.  This  is  equal  to  fifteen 
to  one  in  favor  of  cast-iron.  Other  experiments  by  Mr.  Mallett 
showed  that  cast  iron  unprotected  and  exposed  freely  to  atmospheric 
action  was  corroded  nearly  as  rapidly  as  by  the  action  of  clear  sea- 
water. 

Mr.  Kenniple,  Central  India  Railway  Company,  reports  that 
"the  greatest  corrosion  of  cast-iron  piles  existed  close  to  the  low- 
water  mark,. and  did  not  extend  to  any  considerable  distance  from 
that  point."  This  condition  he  also  found  to  exist  in  the  wrought- 
iron  bolts  and  braces.  After  an  exposure  of  twenty-five  years  the 
piles  were  found  to  be  in  very  good  condition,  and  corrosion  had  only 
occurred  in  places  accessible  for  renewals.  A  thin  coating  of  mud, 
marine  growth,  and  barnacles  upon  the  immersed  surfaces  of  the 
ironwork  that  protected  them  from  contact  with  fresh  supplies  of 


324 


CORROSION  OF  CAST-IRON   CUBES. 


water,  or  from  the  water  in  motion,  had  a  tendency  to  retard  cor- 
rosion, but  when  they  were  removed  corrosive  action  increased  at 
once.  He  concludes  that  after  a  life  of  from  thirty  to  fifty  years 
cast-iron  structures  exposed  to  sea-water  can  only  be  regarded  as  of 
a  temporary  character,  especially  those  of  light  cast-iron  pile  design. 

Dr.  Grace  Calvert,  F.R.S.,*  experimented  on  a  number  of  gray 
cast-iron  cubes  made  of  Staffordshire  cold-blast  iron  immersed  in 
acidulated  water.  The  specimens  were  0.39  inch  cube,  specific  grav- 
ity 7.858,  weight  of  cube  237  grains.  The  cubes  were  placed  sepa- 
rately in  bottles  holding  about  30  cubic  inches  of  greatly  diluted 
sulphuric  acid.  Similar  cubes  were  placed  in  bottles  containing 
dilute  hydrochloric,  acetic,  and  phosphoric  acids.  The  action  of  the 
acids  on  the  iron  was  slow;  but  at  the  end  of  three  months,  although 
the  appearance  of  the  cubes  had  not  changed,  some  of  them,  es- 
pecially those  immersed  in  the  solution  of  acetic  acid,  had  softened 
so  that  a  knife-blade  could  penetrate  them  0.11  to  0.16  of  ^n  inch. 

The  solutions  of  acids  mentioned  were  replaced  by  a  fresh  one  in 
each  bottle  every  two  months  for  two  years.  Changes  were  then 
found  to  have  taken  place  in  all  of  the  cubes,  the  acetic  acid  show- 
ing the  greatest  decomposing  effect,  then  the  hydrochloric,  sulphuric, 
and  phosphoric  acids;  the  latter  had  the  least  effect  upon  the  cubes. 

The  action  of  the  acids  upon  the  iron  had  changed  its  nature, 
without  any  alteration  of  its  bulk  or  in  the  appearance  of  the  sur- 
face of  the  cubes.  The  weight  of  one  cube  after  two  years'  immer- 
sion was  54  grains  against  its  original  weight  of  237  grains.  Its 
specific  gravity  was  2.751  instead  of  7.858.  The  change  in  the  physical 
character  of  the  iron  is  indicated  by  the  following  analysis  of  the 
gray  cast-iron  from  which  the  cubics  were  made,  and  a  set  of  cubes 
-after  a  two  years'  immersion  in  the  acetic  acid  solution: 


Before  Immersion. 

After  Immersion. 

Iron       .       ... 

.   95  413  per  cent. 

79  .  960  per  cent. 

Carbon     

2  900 

11.070 

Nitrogen  
Silicon 

0.790 
0  478 

2.590 
6  070 

Sulphur  

0  179 

0.096 

Phosphorus  
Loss  

0.132 
0  108 

0.059 
0.155 

100.000 

100.000 

*  Minutes  of  Proceedings  of  the  Institute  of  Civil  Engineers. 


CORROSIVE  INFLUENCES  IN  THE  ATMOSPHERE.         325 

Dr.  Angus  Smith  found  that,  taking  the  inland  country  parts 
of  England  as  a  basis  for  the  acidity  of  rain-water  and  the  impurity 
of  the  atmosphere,  and  rating  them  as  0,  in  Glasgow  they  were  83, 
and  in  London  28. 

The  comparative  amounts  of  ammonia  and  other  impurities  in 
the  air  and  in  rain-water  were:  Valentia  1,  Glasgow  50,  Liverpool 
30,  Manchester  36.  For  the  amount  of  hydrochloric_acid  present  in 
the  same  elements  Blackpool  was  100,  London  320,  the  Under- 
ground Railway  in  London  974.  Anhydrous  sulphuric  acid  at 
Blackpool  100,  London  352,  Underground  Railway  1554.  Ammo- 
nia and  albuminoid  ammonia  at  Innellan,  on  Firth  of  Clyde,  100, 
London  108  and  117,  Glasgow  150  and  221,  the  Underground  Rail- 
way 138  and  271. 

Drs.  Clowes  and  Andrews7  examination  of  the  air  in  the  cars  of  the 
Central  London  Railway  showed  a  maximum  amount  of  carbon  dioxide 
of  14.7  volumes  and  a  minimum  amount  of  9.6  volumes  in  10,000  vol- 
umes of  air.  In  a  railway-station  elevator  15.2  volumes  was  found. 

Many  points  in  the  Paris  underground  railway  system  have  33 
volumes  of  carbon  dioxide  in  addition  to  other  deleterious  gases  and 
2  per  cent  of  aqueous  vapor.  Dr.  Clowes  states  that  not  more 
than  8  volumes  of  carbon  dioxide  in  10,000  volumes  of  air  should  ever 
be  present  at  any  point  in  a  railway  building. 

Dr.  Smith  also  found  a  variety  of  solid  substances  in  the  air,  such 
as  common  salt,  sulphur,  nitrate  of  ammonia,  lime  salts,  iron;  also 
the  phosphates,  iodides,  and  other  organic  matters  given  off  by  ani- 
mals, vegetables,  etc.  The  percentage  of  oxygen  in  the  open  air 
varied  from  21.0  to  20.40,  while  the  carbonic  gas  varied  from  its 
normal  amount  of  three  parts  in  ten  thousand  to  over  thirteen  parts 
in  the  London  Underground  Railway,  and  some  parts  of  the  Swiss 
tunnel  contained  over  17  per  cent. 

Dr.  Huxley's  Physiography  gives  his  examination  of  the  amount 
of  carbonic  acid  gas  in  10,000  parts  of  the  atmosphere  at  a  number 
of  points  as  examined  by  him,  viz.: 

On  the  River  Thames  at  London,  mean 3 . 43 

In  the  streets  of  London  "    3 . 80 

Top  of  Ben  Nevis,  Scotland,  4436  feet  high,  mean 3 .27 

A  ward  in  St.  Thomas'  Hospital,  London 4 . 00 

Haymarket  Theatre,  London,  Dress  Circle  at  11.30  P.M.  when 

lighted  by  gas 7 . 57 

Underground  Railway,  London 14 . 52 

Average  of  339  English  mines 78 . 50 

Highest  amount  in  a  Cornish  mine 250 . 00 

See  Chapter  XXXVI  for  corrosive  elements  in  snow-water. 


326  CORROSION  OF  CAST-IRON  PIERS. 

Dr.  W.  G.  Black*  gives  the  results  of  his  examinations  for  dust 
and  soot  in  the  air,  in  the  central  district  of  Edinburgh  during  the 
year  1902.  The  fall  of  dust  and  soot  in  an  open  dish  of  75  square 
inches  area  amounted  to  2  ounces,  equal  to  3.8  ounces  per  square 
foot,  or  23.5  pounds  for  every  100  square  feet. 

The  above  amounts  of  corrosive  elements  are  not  arbitrarily  con-*' 
stant,  but  they  indicate  the  corrosive  influences  that  may  be  encoun- 
tered in  almost  every  situation  of  engineering  work. 

Mr.  Beardmore,  C.E.,  instances  a  case  of  a  sea-lock,  in  which 
soft  water  was  "locked"  down  into  the  sea-water  level.  At  the  end 
of  thirty-five  years'  service  all  of  the  cast-  and  wrought-iron  attach- 
ments to  the  wooden  lock-gates,  also  the  spikes  in  the  platforms  and 
gate-sills,  had  completely  corroded  away,  though  the  timber  parts 
of  the  structure  were  perfectly  sound. 

Ferric  metal  exposed  to  the  action  of  salt  or  fresh  water  which 
is  not  changed  corrodes  far  less  rapidly  than  where  the  water  is 
changed  more  or  less  frequently. 

Dr.  Lyon  of  India,  a  high  chemical  authority,  reports  that 
some  cast-iron  piles,  after  four  and  a  half  years'  exposure  to  the 
action  of  pure  sea-water  having  a  specific  gravity  of  1.028  and  that 
contained  3000  grains  of  solid  matter  per  gallon,  of  which  1605  con- 
sisted of  the  chlorides  of  sodium,  magnesium,  etc.,  had  undergone 
a  change  to  a  depth  of  -^  inch  from  the  surface  of  the  metal. 

The  Milton-on-Thames  pier  was  erected  in  1844  on  cast-iron 
columns  3  feet  in  diameter  and  1J  inches  thick.  In  the  Gravesend 
town  pier  and  the  Maplin  Sands  lighthouse  the  cast-iron  columns 
and  other  cast-iron  members  exposed  to  the  sea-water  were  originally 
If  and  1J  inches  thick.  In  all  of  these  structures,  at  the  end  of  forty- 
five  years,  only  f  inch  of  the  metal  remained  unaffected;  the  rest 
had  changed  to  the  semblance  of  plumbago.  None  of  the  members 
of  these  structures  indicated  any  change  in  the  metal. 

Mr.  Thomas  Rhodes,  C.E.,  reports  that  "in  the  locks  of  the 
Caledonian  Canal  the  cast-iron  sluice-gates  were  exposed  to  sea- 
water.  All  of  the  parts  were  coated  with  a  heavy  Swedish  tar, 
except  on  the  working  faces  of  the  gates.  These  faces  were  faced 
and  ground  together.  Four  years  after  the  immersion  of  the  gates, 
upon  an  inspection  of  their  condition,  on  all  of  the  parts  coated  with 
the  tar  no  corrosion  was  apparent,  while  the  machined  and  ground 

*  Royal  Meterological  Society  Journal,  XXII,  1903,  p.  134. 


CORROSION  OF  CAST-IRON  ARCHES.  327 

working  faces  were  softened  and  changed  to  plumbago  to  the  depth 
of  J  of  an  inch,  and  had  to  be  renewed. " 

The  experience  of  American  engineers  appears  to  be  equally 
conclusive  of  the  treacherous  character  of  cast  iron  exposed  to  sea- 
air  or  sea-water. 

Mr.  John  D.  Van  Buren,  in  a  paper  read  before  the  American 
Society  of  Civil  Engineers,  stated  that  "bolts  and  other  wrought-iron 
parts  are  badly  corroded  in  less  than  twenty-five  years  when  submerged 
in  sea-water.  Certain  kinds  of  cast  iron  could  perhaps  be  made  to  last 
fifty  years,  which  would  be  a  generous  allowance,  and  probably 
greatly  exceeds  the  average  life  of  cast  iron  exposed  to  sea-water." 

Sir  Benjamin  Baker,  in  his  paper  "The  Metropolitan  and  Metro- 
politan District  Railways/'  *  says:  "In  tunnel  constructions  when  the 
roof  members  and  bottom  flange  of  the  girders,  tie-rods,  anchors,  etc., 
are  much  exposed  to  corrosive  influences,  wrought-iron  members 
were  used  and  thought  to  be  more  trustworthy  than  cast  iron,  but 
were  found  to  be  exposed  to  a  greater  risk  from  hidden  oxidation. 
Experience  has  shown  the  trouble  and  cost  of  maintaining  ironwork 
exposed  to  atmospheric  corrosion  in  an  underground  railway.  It  is  so 
great  that  it  would  justify  a  considerable  increase  in  the  first  cost  by 
substituting  brickwork  and  deep  cuttings  for  ironwork  and  shallower 
construction.  Where  the  depth  was  sufficient  for  an  arch,  brick 
covered  ways  were  to  be  preferred  to  iron-girder  constructions,  on 
account  of  the  smaller  cost,  increased  durability,  and  safety." 

Sir  John  Fowler  confirmed  Sir  Benjamin  Baker's  views  in  regard 
to  the  substitution  of  brick  work  and  masonry  fqr  ironwork  in  all  cases 
where  possible,  even  at  a  material  increase  in  the  cost  of  the  work. 
He  thought  the  question  was  not  confined  to  the  relative  rate  of  corro- 
sion of  cast  iron,  wrought  iron,  or  steel,  but  to  the  great  risk  arising 
from  hidden  oxidation  on  important  members  of  walled-in  ironwork. 

These  views  are  corroborated  in  the  experience  of  American 
railways.  The  Pennsylvania  Railway  has  already  replaced  a  num- 
ber of  its  iron  bridges  with  masonry  arches,  and  wherever  possible 
will  continue  the  substitution. 

Carrwheels  made  from  the  best  of  gray  cast  iron  when  immersed 
either  constantly  or  alternately  wet  and  dry,  in  fresh  or  salt  water  in  all 
stages  of  impurity  are  found  to  corrode  faster  in  the  body  part  of  the 
wheel  than  in  the  tread  or  chill,  the  iron  being  identically  the  same 


*  Minutes  of  Proceedings  of  the  Institute  of  Civil  Engineers,  Vol.  LXXXI. 


328  CORROSION  OF  GRAY  CAST-IRON  PIPES. 

in  both  parts  of  the  wheel  and  under  the  same  corrosive  influences. 
The  difference  must  be  attributed  to  the  effect  of  the  chill,  which 
has  changed  the  molecular  formation  of  that  part  of  the  wheel, 
making  it  more  dense  and  of  a  needle-like  or  filamentous  formation, 
that  is  not  so  readily  attacked  by  corrosion  as  the  crystalline  part. 
This  effect  in  car-wheels  is  the  more  noticeable  as  the  body  part  of  the 
wheel  is  covered  with  a  skin  of  the  silicate  protoxide  of  iron,  produced 
by  the  molten  metal  fusing  the  sand  in  the  mold.  There  is  also  a  further 
protection  afforded  by  a  film  of  the  black  magnetic  oxide  of  iron  being 
formed  at  the  same  time  by  the  oxidation  of  the  hot  metal  in  cooling. 
Cast-iron  pipe  or  piles  would  be  more  durable  were  they  cast  from 
chills  the  same  as  the  tread  part  of  a  car-wheel.  Instead,  however, 
of  this  method,  which  is  attended  with  some  difficulties  not  present 
in  the  casting  of  car- wheels,  it  has  been  proposed  to  increase  the 
depth  of  the  silicate  coating  on  such  bodies  by  a  process  used  by  the 
ate  Mr.  E.  F.  C.  Davis,  late  President  of  the  American  Society  of  Me- 
chanical Engineers,  in  the  protection  of  mining  pumps,  chambers, 
and  pipes  subject  to  the  action  of  mine-water.  The  corrosive  action 
of  this  fluid  is  very  great  and  increases  by  motion  and  pressure.  The 
process  consists  of  coating  the  cores  and  other  parts  of  the  mould 
with  a  thin  paste  applied  by  a  brush,  which  increases  the  thickness 
of  the  silicate  coat  to  more  than  double  its  natural  thickness,  and 
can  be  made  still  thicker  by  repeated  applications  of  the  paste  before 
casting.  The  composition  of  the  paste  is,  viz. : 

112  parts  silica. 

44  •    "     calcined  soda  carbonate. 
24      "  "        carbonate  precipitate. 

4      "     boracic  acid. 

Mix  and  thoroughly  pulverize  them.  Coat  the  core  or  mould  with 
plumbago  facing,  and  apply  the  enamel  as  a  powder  or  paste  to  the 
thickness  required,  in  one  or  more  applications,  and  cast  as  usual. 
A  single  coating  with  this  compound  more  than  doubles  the  life  of 
the  metal. 

Fresh  or  sea  water  impregnated  with  decomposing  organic  mat- 
ter, or  acids  and  chlorides  discharged  from  bleacheries,  paper-mills, 
etc.,  hastens  corrosion,  which  is  increased  by  motion,  pressure,  and 
high  temperature. 

The  Merrimac  River,  at  Lowell,  Mass.,  is  affected  to  such  an  ex- 
tent by  the  discharge  waters  from  manufactories,  that  during  the 
ordinary  flow  of  the  river  in  summer,  it  will  change  litmus  paper. 


CORROSION  OF  GRAY  CAST-IRON  AND  CANNON.         329 

Instances  are  on  record  where  firm  gray  cast-iron  water-pipes  of 
large  diameter  and  1  inch  in  thickness,  conveying  sea-water,  have 
inside  of  five  years  changed  to  a  plumbago-like  substance,  that  had 
hardly  any  strength  and  could  be  cut  easily.  No  change  in  the  appear- 
ance of  the  metal  was  indicated ;  the  change  in  the  metal  was  from  the 
inside,  or  where  in  contact  with  the  water.  The  pipes  had  the  usual 
tough  skin,  and  were  nominally  protected  by  a  foundry  dip  coating. 

Mr.  F.  A.  Boyer,  M.E.,*  reports  that  a  cast-iron  water-pipe  12  inches 
in  diameter,  1200  feet  long,  used  to  circulate  sea- water  for  conden- 
sation purposes,  laid  mostly  in  the  open  air,  was  changed  in  two  and 
one-half  years  to  a  plumbago-like  substance  that  could  be  cut  easily, 
but  to  the  eye  presented  no  indications  of  the  change  in  the  metal. 

Gray  cast-iron  water-pipes  f  laid  at  Atlantic  City,  N.  J.,  for  nine- 
teen years,  in  black  swamp-mud  containing  decomposed  vegetable 
and  saline  substances  highly  acidulous  and  corrosive,  were  found 
to  be  generally  corroded  externally.  The  iron  was  softened  about 
i  inch  in  depth,  and  in  many  places  it  had  extended  through 
the  pipe.  The  corroded  metal  appeared  to  have  been  replaced  by 
a  clay-like  substance  of  light  weight,  containing  17  per  cent  of  silica, 
particles  of  the  cast  iron  being  embedded  in  it. 

A  member  of  the  American  Water-works  Association  reported 
in  the  1902  meeting  the  decay  of  two  cast-iron  suction-pipes,  where 
the  metal  was  changed  to  a  graphitic  substance,  easily  cut.  The  suc- 
tion water  was  originally  soft  ground-water,  but  later  was  artesian 
well-water,  containing  a  small  amount  of  sulphuretted  hydrogen. 
Wherever  brass  and  iron  came  in  contact  with  the  water-mains, 
eventually  the  iron  became  soft  enough  to  cut  easily. 

Mr.  Trautwine,  an  eminent  American  civil  engineer,  recommends 
a  white  close-grained  cast  iron  or  chilled  iron  for  piles  and  wharfs 
exposed  to  sea-water  or  sea  air. 

Mr.  Turner,  Assoc.  R.S.M.,  recommneds  a  gray  cast-iron  for 
docks  and  piles  exposed  in  English  sea  locations. 

The  above  results  of  the  use  of  different  brands  of  cast  iron  for 
sea-air  and  sea-water  exposures  in  different  locations  are  probably 
due  to  the  difference  in  sea-water  in  different  parts  of  the  world. 
Sea-water  varies  greatly  in  corrosive  and  fouling  properties  even  if 
not  contaminated  as  mentioned  before. 

*  Transactions  American  Society  of  Mechanical  Engineers,  Vol.  XVI,  1894. 
Paper  No.  626,  p.  416. 

f  Prof.  W.  P.  Mason,  Troy  Polytechnic  Institute,  Troy,  N.  Y. 


330      RATE  OF  CORROSION  BETWEEN  IRON  AND  STEEL. 

Cannons  and  other  tough  cast-iron  articles,  6  or  more  inches 
in  thickness  of  metal,  sunk  in  the  sea  in  many  parts  of  the  world, 
change  in  about  one  hundred  years  to  a  soft  carburet  of  iron  or  a 
plumbago-like  substance,  without  any  diminution  in  size  or  any 
exfoliation  in  scales  or  .flakes,  as  in  atmospheric  oxidation.  They 
become  too  hot  to  handle,  when  first  raised  and  exposed  to  the  air, 
from  the  absorption  of  oxygen. 

Mr.  Francis  T.  Bowles,  Naval  Constructor  United  States  Navy, 
states:  "That  the  corrosion  of  iron  and  steel,  from  the  observations 
made  at  the  different  Government  navy-yards,  with  the  different  kinds 
of  iron  and  steel  used  in  naval  vessels  exposed  to  sea-water  in  various 
parts  of  the  world  under  a  great  number  of  conditions  of  tempera- 
ture, brackish,  sewage,  and  dock  water,  was:  That  unpainted  iron 
and  steel  plates  will  corrode  in  one  hundred  years  on  each  exposed 
surface  .30  to  .50  inch  of  metal;  in  ordinary  fresh  water,  .02  to 
.03  inch,  and  in  the  atmosphere,  .25  to  .30  inch."  But  he  makes  no 
distinction  in  the  rate  of  corrosion  between  iron  and  soft  steel. 

Mr.  L.  M.  Hastings,  City  Engineer,  Cambridge,  Mass.,  reporting 
the  results  of  his  experiments  to  ascertain  the  difference  in  corro- 
sion between  wrought  iron,  soft  steel,  and  cast  iron,  all  uncoated, 
exposed  to  a  running  mixture  of  pond  and  brook  water,  fairly  soft 
and  comparatively  free  from  any  acid  or  saline  matters,  states:  "That 
after  an  exposure  of  one  year  the  uncoated  wrought  iron  was  badly 
tuberculated  and  rusted,  the  soft  steel  was  similarly  affected,  but 
not  to  the  same  degree;  the  cast  iron  was  also  affected.  The  per- 
centages of  increase  in  weight  due  to  corrosion  were  as  follows:  The 
wrought  iron,  1.5  to  3.1  per  cent;  the  steel,  1.1  to  2.1  per  cent,  and 
the  cast  iron,  1.0  to  0.96  per  cent.  A  similar  set  of  plates  buried 
in  sand,  also  in  clay  soil,  showed  the  same  relative  difference  in  cor- 
rosion of  the  metals." 

Dr.  Robert  H.  Thurston*  reports  the  result  of  his  investigations 
of  the  different  rates  of  corrosion  between  iron  and  steel.  Briefly, 
they  are:  "Cast  iron  in  dilute  solutions  of  acids  is  rapidly  acted 
upon,  the  metal  retaining  its  general  appearance  unchanged. 
The  condensation  waters  from  engines  are  strongly  corrosive.  Hard 
iron,  rich  in  combined  carbon,  rusts  slowly.  Graphitic  iron,  also 
different  qualities  of  iron  in  contact,  increases  the  rate  of  oxida- 
-tion  presumably  by  forming  local  voltaic  couples.  Hard  steel 

*  "Materials  of  Engineering/'  See.  192,  Vol.  II,  pp.  328  et  seq. 


RATE  OF  CORROSION  BETWEEN  IRON  AND  STEEL.       331 

rusts  less  rapidly  than  soft  steel.  Bilge-water  corrodes  iron  and 
steel  rapidly.  Iron  ships  carefully  painted  have  been  found  to  cor- 
rode at  a  rate  not  far  from  ^  inch  in  twenty-five  years." 

Thwaite*  gives  a  formula  and  table  of  constants  for  the  rate  of 
corrosion  between  different  metals  under  different  elemental  expo- 
sures, all  for  unprotected  metal,  viz.: 


Material. 

Water. 

Impure  Air. 

Sea. 

River. 

Foul. 

Clear. 

Foul. 

Clear  Water, 
or  in  Air. 

Cast  iron  
Wrought  iron  

0.0656 
.1956 
.1944 
.23 
.09 

0.0636 
.1255 
.0970 
.0880 
.0359 

0.0381 
.1440 
.1133 
.0728 
.0371 

0.0113 
.0123 
.0125 
.0109 
.0048 

0.0476 
.1254 
.1252 
.0854 
.0199 

Steel  

Cast  iron,  no  skin.  .  . 
Galvanized  iron.  .  .  . 

Average  for  sea-water:  Cast  iron,  in  contact  with  brass,  copper,  or  gun 
bronzes,  0.19  to  0.35;  wrought  iron,  in  contact  with  the  same,  0.3  to  0.45. 

No  analysis  of  the  constituents'  of  the  several  metals  is  given,  and 
the  terms  hard  and  soft  metal  are  very  variable  conditions.  How- 
ever, all  of  the  above  experimenters  give  hard  metal,  whether  of 
cast  iron,  wrought  iron,  or  steel,  as  being  less  corrosive  than  soft 
metal. 

Mr.  Thomas  Andrews,  F.R.S.,  experimented  at  the  Wortley  Iron 
Works  on  wrought-iron  and  steel  plates  containing  varying  amounts 
of  carbon.  The  plates  were  immersed  m  sea-water  that  was  changed 
monthly.  It  was  found  that  the  lower  the  percentage  of  combined 
carbon  in  the  metal,  the  lower  was  the  corrosion.  The  best  wrought 
iron  corroded  less  than  any  of  the  steels  at  any  stage  of  their  expo- 
sure during  the  one  hundred  and  ten  weeks  of  the  test.  Wrought 
iron  that  contained  double  the  usual  amount  of  phosphorus  and 
manganese  corroded  more  than  the  iron  free  from  these  substances, 
but  the  corrosion  in  them  was  less  for  the  whole  period  of  the  test 
than  in  any  of  the  steels,  with  the  single  exception  of  a  very  soft 
Bessemer. 


*  Engineering  News,  Nov.  3,  1898. 


332  CORROSION  OF  WROUGHT-1RON. 

In  any  of  the  steels,  manganese  in  excess  tended  to  produce  an 
increased  corrosion,  evidently  from  its  unequal  distribution  and 
the  galvanic  action  on  the  adjacent  metal. 

On  the  whole,  from  the  many  reported  cases  of  corrosion  in  all 
parts  of  the  world,  that  include  many  qualities  of  cast  iron  and 
wrought  iron  that  have  had  approximate  exposures  for  thirty  or 
more  years,  it  appears  that  hard  close-grained  and  chilled  iron  are 
less  liable  to  corrode  than  any  brands  of  softer  metal.  Bessemer, 
open-hearth  steels,  also  steel  castings  used  for  structural  work,  have 
not  yet  had  time  enough  to  afford  many  comparisons  with  each  other, 
or  with  cast  iron  and  wrought  iron,  to  prove  which  metal  is  the  most 
affected  by  corrosion. 

It  is  left  to  the  future  to  develop  some  alloy  of  iron  or  steel  that 
will  retard  if  not  prevent  corrosion,  while  not  materially  reducing 
their  strength  or  other  qualities. 

The  composition  of  wrought  iron  and  the  processes  it  is  subjected 
to  between  the  bloom  and  finished  article  have  a  great  effect  to 
determine  its  rate  of  corrosion.  Iron  containing  sulphur  is  red  short, 
that  containing  phosphorus  is  cold  short.  Both  differ  in  corrosi- 
bility;  the  cold  short  is  the  one  less  affected,  being  harder  and  more 
crystalline  in  composition,  while  the  red  short  has  the  sulphur  ele- 
ment to  aid  corrosion.  Neutral  iron  made  from  both  of  the  above 
brands  has  a  different  rate  of  corrosion  than  either. 

The  same  quality  of  iron  worked  in  the  rolls,  in  the  one  case  both 
lengthwise  and  crosswise,  to  produce  sheet  or  plate  iron,  differs  in 
corrosibility  from  that  worked  principally  in  one  direction,  as  in 
the  case  of  beams,  angles,  and  other  structural  shapes.  All  of  the 
latter  forms  tend  to  disintegrate  by  corrosion  into  strips,  needle 
or  fibrous  form,  owing  to  the  granular  character  of  the  iron  being 
changed  t?y  the  rolls  into  parallel  fibres,  that  are  not  interlocked 
as  the  cross-rolling  arranges  them.  The  corrosion  aided  by  the 
cinder  follows  the  grain  of  the  metal.  The  cinder  is  acid  and  porous, 
and  only  in  mechanical  bond  with  the  iron  by  reason  of  the  action 
of  the  rolls. 

Fig.  47  shows  the  effect  of  laminated  corrosion  of  a  steel-plate 
girder  on  the  Washington  Street  railway  bridge  in  Boston.  Wrought- 
iron  pipe  used  for  water,  steam,  and  gas  service  is  an  example  of 
this  make  of  iron.  It  corrodes  more  rapidly  than  the  same  quality 
of  iron  in  bars.  The  iron  is  not  so  condensed  in  the  process  of  roll- 
ing a  tube  as  in  rolling  a  bar.  The  tube  skelps  receive  their  principal 


CORROSION  OF  WROUGHT-IRON. 


333 


of  a  steel-plate  girder  on  the 
Washington  Street  railway 
bridge  in  Boston. 


rolling  lengthwise,  while  bar  iron  gets  some  edge-rolling  in  passing 
through  the  rolls.  Enough,  in  fact, 
to  show  a  marked  difference  in  the 
corrosion  of  the  two  products,  when 
from  the  same  metal.  Boiler-tube 
skelps,  being  made  from  a  better 
quality  of  iron,  or  having  been  re- 
fined by  a  further  working  of  the 
same  grade  of  metal,  by  having  had 
some  cross-rolling  before  being  made 
into  skelps,  are  less  affected  by  cor- 
rosion than  ordinary  wrought-iron 
pipes.  The  arger  sizes  of  these  pipes 
being  made  from  long  rolled  skelps 
and  lap- welded,  instead  of  only  welded, 

as  in  the  case  of  small  pipes,  show  in    FIG.  47. — Laminated    corrosion 
the  welds  a  less  corrosibility  than  in 
the  body  part  of  the  pipe.     This    is 
due  to  the  additional  condensation  of 
the  fibres  at  the  welds;  also  there  is  less  cinder  in  the  lap- weld. 

Cold-rolled  shafting  and  rods  are  rendered  more  dense  by  the 
rolling  process,  and  they  are  less  affected  by  corrosion  than  the  bars 
from  which  they  are  cold-rolled.  The  process  also  increases  their 
tensile  strength.  Cold-drawn  wire  also  presents  the  same  features. 
A  wire  nail  corrodes  less  than  a  cut  nail,  so  does  a  hammered  or  so- 
called  wrought  nail. 

Polished  iron  and  steel  tools,  sword-blades,  razors,  etc.,  resist 
corrosion  better  than  the  same  articles  ground,  but  not  polished; 
the  improved  resistance  being  due  to  the  surface  not  having  so  many 
small  cavities  to  hold  any  moisture  reaching  it,  because  of  the  con- 
densed and  repellent  nature  of  the  surface  due  to  the  polishing. 

Burnished  surfaces  resist  corrosion  and  are  more  repellent  of 
moisture  than  polished  ones;  but,  if  corrosion  is  once  established 
on  them  as  a  spot,  it  appears  to  concentrate  an  energy  to  produce 
a  deep  corrosion,  that  is  difficult  to  eradicate. 

Rivets  have  a  different  rate  of  corrosion  between  their  heads, 
or  points,  than  the  body  of  the  rivet.  Corrosion  of  a  riveted  joint 
generally  concentrates  its  action  more  immediately  around  the  rivet 
heads  and  points,  than  on  them,  forming  a  pit  or  seam  furrow.  A 


334  CORROSION  OF  TEE  BEAMS  AND  ANCHORS. 

number  of  disastrous  failures  of  important  ferric  structures  have 
occurred  from  this  type  of  corrosion. 

The  quantity  of  metallic  iron  in  the  best  refined  brands  is  99.8 
per  cent.  In  common  bar  iron  it  is  98  to  98.3  per  cent.  In  ordinary 
cast  iron,  about  93.5  per  cent,  and  2.5  per  cent  of  graphitic  carbon. 

The  porosity  of  volume  in  ordinary  cast  iron  is  1.41  per  cent;  in 
different  kinds  of  Bessemer  steel,  0.41  to  1.20  per  cent.  In  a  loco- 
motive tire  ingot,  0.57  per  cent.  For  a  hard  iron  tire,  0.97  per  cent. 
In  a  basic-iron  rail  ingot,  1.95  per  cent.  In  a  basic-steel  ingot,  1.22 
to  2.17  per  cent. 

At  an  annual  convention  of  the  American  Institute  of  Architects, 
in  a  discussion  on  the  use  of  iron  and  steel  in  the  construction  of 
modern  high  buildings,  it  was  reported  by  one  of  the  leading  archi- 
tects in  the  United  States  that  the  iron  beams  removed  by  him  from 
the  old  Times  building,  though  in  use  only  thirty-five  years,  were 
rotten  with  rust.  They  were  enclosed  in  eight  inches  of  brickwork, 
forming  the  arches  that  supported  the  pavement  over  the  vault 
where  the  steam-boilers  were  placed,  and  though  always  dry,  yet 
had  been  exposed  to  ordinary  fire-room  vapors.  They  had  been  well 
painted  with  iron-oxide  paints  and  protected  from  external  moisture 
by  an  asphalt  covering.  The  iron  came  off  in  strips,  clearly  show- 
ing that  the  rust  had  followed  the  lamination  of  the  iron,  the  web 
of  the  girders  being  so  rotten  as  to  be  easily  broken  by  the  fingers. 
Other  examples  of  sidewalk  beam  corrosion  are  given  on  page  269. 

Anchor-stocks  made  from  hammered  iron  always  show  less  corro- 
sion than  cable  links.  In  both  cases  only  the  best  quality  of  iron, 
that  contains  but  a  small  quantity  of  cinder,  is  employed.  The 
link  corrosion  is  in  the  form  of  strips,  following  the  fibre  of  the  metal, 
while  the  anchor-stock  generally  corrodes  in  a  compact  scale  form. 
A  different  rate  of  corrosion  exists  in  the  cable  links  at  the  end,  where 
they  are  welded  from  that  shown  in  the  body.  The  iron  in  or  near  the 
weld  is  refined  and  more  dense,  also  has  the  fibres  interlaced;  all 
these  points  have  a  tendency  to  delay  corrosion,  which  is  more  rapid 
where  the  fibres  are  undisturbed  by  the  hammer. 

Tunnel  Shields  and  Submarine  Metal  Corrosion. 

With  the  recorded  instances  of  the  corrosion  of  iron  and  steel  to 
judge  from,  it  may  be  pertinent  to  ask,  how  long  will  the  metal  lining 
of  submarine  tunnels  last?  Notably,  those  laid  in  sea-silt  or  ocean 
mud.  The  integrity  of  the  brick  lining  is  wholly  dependent  upon 


CORROSION  OF   TUNNEL  SHIELDS.  335 

the  metal  shield  put  in  place  as  the  work  progresses,  and  without 
which  the  construction  of  the  tunnel  would  be  impossible.  Even 
when  completed,  these  constructions  have  a  small  margin  of  strength 
above  that  necessary  to  get  the  metal  into  place  during  construc- 
tion, and  none  at  all  as  a  reserve  for  the  loss  in  strength  from  the 
inevitable  change  in  the  metallic  work  exposed  to  sea-water,  which 
begins  just  as  soon  as  the  shield  is  in  place;  and  in  the  case  of  tough 


FIG.  48. — Corrosion  of  a  steel  plate  from  the  Washington  Street  railway  bridge 

in  Boston. 

close-grained  cannon  metal,  has  been  ascertained  to  be  at  a  rate  of 
about  six  inches  in  one  hundred  years. 

The  lining  plates  and  ribs  for  tunnel-shields  are  seldom  over 
three  inches  thick.  The  different  sections  of  the  shield  utterly  pre- 
clude any  material  strength  to  be  derived  from  their  circular  form, 
made  with  bolted  joints.  The  bolts  holding  the  shield  sections 
together  and  to  each  other  are  relatively  small,  and  will  be  the  first 
to  yield  to  the  effects  of  saline  corrosion. 

The  brickwork  or  concrete  lining  of  the  tunnel,  however  thick, 
or  the  thin  coat  of  partly  dried  paint,  will  not  protect  the  shield 
metal,  for  any  appreciable  time,  from  the  change  to  a  plumbago-like 
substance,  which  does  not  require  the  presence  of  air  to  produce  it. 
The  passage  of  railway  trains  through  the  tunnel  will  set  up  an  undu- 
lating or  vibratory  movement  through  the  tube  resting  on  its  bed 
of  salt  silt,  like  a  log  of  wood  in  a  mill-pond,  being  hardly  more  resist- 


336 


CORROSION  IN  TUNNELS. 


ant  to  a  change  of  position  from  any  force,  and  relatively  not  a  hun- 
dredth part  as  strong. 

However  strong  such  metallic  shields  and  masonry-lined  con- 
structions are  when  driven  through  rock  or  earth,  in  or  through 
salt  water  or  the  saturated  silt  of  salt  water,  they  are  the  most 
treacherous  and  dangerous  of  all  engineering  devices  yet  conceived, 
affecting  the  transportation  and  safety  of  the  public. 

Metallic  salts  and  acids  in  water  intensify  the  corrosion  of  all 
metals  exposed  to  their  action  either  by  immersion  or  by  condensa- 
tion of  the  vapors  from  them.  The  metal- work  of  railway  tunnels  is 
disastrously  affected  by  the  condensed  vapors  of  sulphurous  and  car- 
bonic acid  and  the  moisture  due  to  such  locations,  the  corrosion 
of  the  metals  decreasing  the  resistance  of  the  water  to  voltaic  circuits; 
this  corrosion  by  liquids  being  voltaic  phenomena  in  all  cases,  and 
in  many  cases  is  intensified  by  the  moisture  being  in  the  form  of 
drops  instead  of  being  uniformly  spread  over  the  whole  surface. 

The  cut  (Fig.  49)  from  the  Railroad  Gazette,  November  23, 
1894,  represents  a  section  of  a  seventy-six-pound  tee-rail  laid 
in  the  Musconetcong  Tunnel,  removed  after  '  being  laid 
five  years,  having  lost  more  weight  by  corrosion  than  wear. 
The  dotted  lines  show  the  original  size  of  the  rail,  and 
the  full  lines  its  present  worn 
and  corroded  size,  which  is  very 
marked.  The  rails  were  removed 
on  account  of  their  strength  having 
been  seriously  affected  by  the  cor- 
rosion. The  tunnel  is  very  damp, 
and  a  great  deal  of  sand  is  used 
by  the  engines,  which  kept  the 
base  of  the  rail  covered,  the 
vibration  caused  by  the  passage  of 
the  trains  having  a  tendency  to 
rernove  the  thin  scale  of  rust  almost 
as  rapidly  as  it  could  be  formed. 
There  was  but  little  apparent  dif- 
ference in  the  corrosion,  whether 
between  the  cross-ties  or  where  the 

rail  rested  upon  them.  The  flanges  of  the  wheels  removed  the  rust 
as  it  formed  on  the  side  and  top,  leaving  a  clean  surface  that  would 
sensibly  corrode  between  the  intervals  of  the  trains. 

In  the  St.  Gothard  Tunnel,  49,168    feet    long,  the  air    remains 


FIG.  49. 


CORROSION  IN  TUNNELS.  337 

almost  motionless  for  twelve  hours  per  day,  and  though  the  accu- 
mulation of  carbonic  acid  is  rapid,  and  a  part  of  it  is  absorbed  by 
the  great  quantity  of  water  present,  the  air  is  almost  unrespirable, 
and  causes  a  great  deal  of  distress  to  the  workmen,  and  the  corrosion 
of  all  metal-work  inside  the  tunnel  is  very  rapid. 

The  water  that  trickles  down  the  walls  of  the  tunnel  is  the  conden- 
sation of  the  exhaust  gases  from  the  locomotives.  It  contains  sul- 
phuretted hydrogen,  sulphur  dioxide, ammonia,  and  carbon  dioxide,  and 
other  combustion  gases.  The  rails  are  renewed  every  ten  years,  and  the 
telegraph  cables  in  the  tunnel  require  exceptionally  strong  wrappings. 

In  the  new  Simplon  Tunnel,  64,718  feet  long,  forced  draft  is 
proposed,  requiring  over  500  H.  P.  at  the  ventilator  shaft.  The 
fans  render  an  effective  duty  of  65  per  cent,  1760  cubic  feet  of  air 
per  second  being  required  for  ventilation. 

In  general,  the  corrosion  of  metals  in  tunnels  where  the  rails  are 
bedded  on  cast-iron  chairs  is  represented  by  cast  iron,  100;  wrought 
iron,  129;  steel,  133. 

In  the  Arlberg  Tunnel,  33,587  feet  long,  the  corrosion  of  the 
rails  and  other  metals  is  so  rapid,  that  they  all  require  renewal  every 
ten  years.  The  corrosion  comes  principally  from  the  condensed 
gases  of  the  locomotives,  though  the  traffic  is  light  and  a  good  qual- 
ity of  coal  is  used.  The  temperature  of  the  tunnel  remains  almost 
uniformly  75°  F.  throughout  the  year. 

The  amount  of  free  sulphuric  acid  in  the  exhaust  gases  from  tun- 
nel locomotives   using  a  good  quality  of  bituminous   coal  has  been 
found  to  be  about  5  pounds  per  hour,  varying  from  -0.3  to   +  7.9- 
per  cent. 

In  a  tunnel  in  France  2850  feet  long,  where  but  little  water  came 
through  the  walls,  "the  78-pound-per-yard  rails  were  replaced  after 
the  passage  of  230,000  trains  at  a  speed  of  nineteen  miles  per  hour. 
They  had  been  eleven  and  one-half  years  in  service  and  had  lost  in 
weight  18|  pounds,  or  24.166  per  cent  per  yard.  The  corrosion  was 
general  over  their  whole  surface,  but  the  rolling  action  of  the  wheels 
on  the  head  increased  the  corrosion  at  that  point  by  keeping  the 
metal  bright  and  removing  the  rust  as  fast  as  it  formed. 

Rolled-steel  cross-ties  for  the  Indian  State  Railway,  laid  in  soil 
that  was  not  actively  corrosive,  at  the  end  of  ten  years  had  not 
corroded  to  any  greater  extent  than  the  rails  laid  on  them. 

In  other  locations  where  steel  cross-ties  were  embedded  in  soil 
containing  .  sea-sand  and  saltpetre,  both  highly  corrosive,  the  rails 
and  cross-ties  were  heated  to  300°  F.  and  immersed  in  a  hot  bath 


338 


CORROSION  OF  TEE  RAILS  ON  DOCKS. 


of  3  parts  of  coal-tar  pitch  and  1  part  of  petroleum  dead  oil. 
This  coating  was  firm  and  tough,  and  did  not  flake  or  scale  off  in 
transportation  or  in  the  laying  of  the  rails.  At  the  end  of  twenty 
years  the  metal  had  not  corroded  to  any  appreciable  extent,  except 
where  mechanically  injured.  This  coating  was  practically  the  coal- 
tar  dip  used  on  water-pipes  by  English  founders. 

Mr.  Otto  Herting  cites  the  instance  of  the  corrosion  of  some 
tee-rails  used  as  girders  in  a  Cape  Breton  mine,  that  had  been  aban- 
doned twenty  years.  The  metal  was  changed  to  a  grayish-brown 
color,  could  be  cut,  and  had  a  specific  gravity  of  only  2.053.  The 
metal  powdered  in  a  mortar  was  magnetic.  It  analyzed  as  follows: 

Iron 31 . 50  per  cent. 

Graphitic  carbon 24. 10  " 

Silicon 14.20  " 

Manganese 1.93  " 

Sulphur 1.00 

Phosphorus 5.85 

Undetermined  and  loss.  .  21.42  " 


100.00       g  " 

Fig.  50  represents  the  corrosion  of  steel  rails  laid  upon  docks 
and  other  places  contiguous  to  sea-water,  where  the  effect  of  cor- 
rosion was  equal  to  about  4  per 
cent  each  year  upon  the  weight  of  a 
32-pound  rail  per  yard.  The  details 
of  the  rail  from  which  the  cut  was 
made  were  contributed  by  Mr.  Del- 
prat,  Chief  Engineer  of  the  Sumatra 
State  Railway,  through  Mr.  J.  W. 
8  Post,  Divisional  Chief  Engineer  of 
the  Netherlands  State  Railway. 

The  annual  report  for  1900*  of 
the  Samarang-Joana  Steam  Tram- 
way Company  (of  Java)  states 
that  a  considerable  number  of  steel 
rails  had  to  be  removed  from  the 
harbor  tracks  on  account  of  cor- 

FIG.  50.— Rail  section  of  the   Su-  rosion,  which  amounted  to  10.7  kilos 
matra      Railway,      showing     the 

effect  of  corrosion  by  sea-water  in  per  meter, 
ten  years.  Mining   metal  is  exposed  to  se- 

*  Engineering  News,  November  21,  1901. 


CORROSION  IN  MINES.     THERMO-ELECTRIC  ACTION.      339 

vere  corrosion  from  many  sources,  the  presence  of  sulphurous  water 
from  decomposed  pyrites  and  other  minerals,  aided  by  heat,  inten- 
sifying the  action. 

Thermo-electric  currents  arise  from  changes  in  temperature  and 
set  up  voltaic  action  which,  though  slight  and  not  easily  detected, 
will  enlarge  all  fissures,  cavities,  and  seams  sufficient  to  sap  the 
strength  of  the  metal. 

Dr.  Henry  Wurtz  *  proposes  an  electro-chemical  process  for 
protecting  mine  metal,  by  connecting  all  of  the  fixed  metal  in  the 
mining  plant  as  the  negative  element,  with  a  dynamo  of  sufficient 
force  to  overcome  the  galvanic  energy  of  the  surfaces  when  exposed 
to  the  mine's  corrosive  liquids,  the  positive  terminal  to  be  con- 
nected to  a  mass  of  hard  coke  in  the  mine  sump.  These  conditions 
vary  but  slightly  from  those  existing  in  a  ship,  and  it  is  not  improb- 
able that  both  systems  could  be  made  to  work  effectively. 

In  a  number  of  instances  where  the  whole  system  of  mining-pipes 
required  renewal  every  two  years,  corrosion  was  completely  stopped 
by  coating  them  with  an  enamel  in  the  following  manner: 

'The  pipes  were  first  pickled  in  a  bath  of  hydrochloric-acid  solu- 
tion to  free  them  from  the  foundry  scale,  then  washed  thoroughly, 
and  dried.  The  pipes  then  received  a  coating -of  34  parts  of  silica, 
2  parts  of  soda,  and  15  parts  of  borax.  These  were  mixed  in 
a  little  water  and  the  pipes  exposed  for  ten  or  fifteen  minutes 
in  a  dull  red-hot  retort.  A  second  coating  was  applied,  composed 
of  34  parts  of  feldspar,  19  parts  of  silica,  24  parts  of  borax,  16  parts 
of  oxide  of  tin,  4  parts  of  fluor  spar,  9  parts  of  soda,  and  3  parts  of 
saltpetre.  These  were  melted  together  in  a  crucible.  When  cold  the 
mass  was  ground  to  a  fine  paste  in  a  little  water  and  applied  to  the 
pipes  with  a  brush.  The  pipes  were  then  exposed  in  a  muffle  to  a 
white  heat.  The  enamel  so  formed  thoroughly  united  with  the  iron, 
and  has  protected  the  pipes  for  over  forty  years,  and  they  are  appar- 
ently in  a  good  condition  now. 

The  Journal  of  the  Society  of  Chemical  Industry  (London),  Febru- 
ary 28,  1894,  details  some  experiments  upon  the  galvanic  action  of 
sea-water  upon  iron  and  steel  structures  in  various  relations  with 
each  other,  as  constructive  parts  of  trusses,  boilers,  etc.,  to  prevent 
the  corrosion.  The  use  of  zinc  and  other  easily  oxidized  metals 
and  alloys  is  suggested,  to  be  so  placed  and  connected  to  the 

*  "Preservation  of  Metals  from  Corrosion  by  Electric  Polarization."  Engi- 
neers' Magazine,  Vol.  VII,  No.  3,  May,  1894. 


340  CORROSION  OF  METALS. 

structure  that  they  will  form  the  electro-positive  element  of  the 
ever-present  galvanic  circuit,  and  by  their  decomposition  protect 
the  structure,  or  at  least  aid  the  paint  coating  in  its  mission  of  pro- 
tection. 

These  protective  features,  proposed  for  the  internal  parts  of  a 
ship,  do  not  apply  to  the  protection  of  the  external  surfaces,  where 
an  entirely  new  set  of  conditions  are  in  force,  owing  to  the  numer- 
ous rivets  employed  to  hold  the  plates  together  and  to  the  frames, 
and  which  are  necessarily  unprotected  from  the  many  sources  of 
corrosion  herein  mentioned. 

Professor  V.  B.  Lewes  *  of  the  Royal  Naval  College,  Greenwich, 
England,  at  a  recent  meeting  of  the  Institute  of  Naval  Architects, 
London,  states: 

"The  rusting  of  iron  and  steel  is  a  definite  chemical  process, 
due  to  the  conjoint  action  of  air,  moisture,  and  carbon  dioxide  upon 
the  metal.  The  increased  rate  of  chemical  corrosive  action  due  to 
a  local  increase  of  temperature  is  noticeable,  and  may  be  due  to 
galvanic  action  set  up  between  portions  of  the  same  metal  at  differ- 
ent temperatures. 

"It  is  an  undoubted  fact  that  the  double  bottom  of  ship  plates 
near  the  boilers  corrodes  more  rapidly  than  similar  plates  in  other 
parts  of  the  vessel,  and  the  increase  in  temperature  near  the  boiler 
is  the  only  factor. 

"It  is  also  noteworthy  that  the  plates  at  the  bottom  of  the  cellular 
spaces  which  are  kept  cool  by  contact  with  the  sea-water  do  not 
corrode;  and  cases  are  noted  in  which  parts  of  a  plate,  which  get 
locally  warmer  than  other  parts — although  the  difference  can  only  be 
a  few  degrees — corrode  much  more  rapidly  than  the  cooler  portions. 

"Experiments  show  that  the  rapid  corrosion  found  in  the  double 
bottoms  near  the  boilers  or  other  sources  of  heat,  is  due  to  galvanic 
action,  and  not  to  the  increased  chemical  activity  due  simply  to 
the  increase  of  temperature.  As  the  ashes  are  drawn  and  quenched 
with  sea- water  near  these  exposed  plates,  no  doubt  some  of  the  corro- 
sion can  be  traced  to  the  gases  thus  formed ;  the  sulphur  in  the  ashes 
also  contributing  its  effect/' 

Mr.  William  Thomson,  F.R.S.,  read  a  paper  on  "The  Influence 

*  A  paper  read  at  the  thirtieth  session  of  the  Institution  of  Naval  Architects 
by  Prof.  Vivian  B.  Lewes,  F.R.S.,  F.I.G.,  Royal  Naval  College  Associate,  April 
12,  1889;  and  published  in  full,  Scientific  American  Supplement,  Vol.  XXVIII, 
No.  709,  August  3,  1889;  pp.  11,  320. 


CORROSION  OF  METALS  IN  CONTACT.  341 

of  Some  Chemical  Agents  in  Producing  Injury  to  Iron  and  Steel," 
before  the  Manchester  Association  of  Engineers,  November  25,  1893, 
in  which  he  refers  to  the  interesting  and  exhaustive  experiments 
made  by  Mr.  Thomas  Andrews,  F.R.S.,  on  the  galvanic  action  which 
takes  place  between  iron  and  steel,  and  between  iron  of  different 
kinds  and  steel  of  different  kinds,  viz.: 

"The  galvanic  action  between  wrought  iron,  cast  metals,  and 
various  steels  during  long  exposures  in  sea-water."  Institute  of 
Civil  Engineers,  Vol.  1883-84,  Part  III. 

"Corrosion  of  metals  during  long  exposures  in  sea-water."  Insti- 
tute of  Civil  Engineers,  Vol.  LXXXII,  1884-85,  Part  IV. 

"The  relative  electro-chemical  positions  of  wrought  iron,  steel, 
cast  metals,  etc.,  in  sea- water  and  other  solutions."  Royal  Society 
of  Edinburgh,  Vols.  1883-1889. 

Mr.  David  Phillips's  paper.     Institute  of  Marine  Engineers,  1890. 

In  the  above-named  articles  Mr.  Andrews  shows  that  while  some 
varieties  of  iron  and  steel  remain  constantly  electro-positive  or  electro- 
negative to  each  other,  others  change,  taking  opposite  positions  toward 
each  other,  while  others  again  change  positions  constantly  during  long 
periods,  these  changes  always  producing  rust. 

"It  can  be  easily  understood  that  while  there  is  no  material  voltaic 
action  between  two  pieces  of  steel  or  two  pieces  of  iron,  or  of  pieces 
of  steel  and  iron,  there  may  be  conditions  on  the  surface  of  one  plate 
or  rivet  which  may  act  strongly  as  an  electro-negative  element,  and 
produce  rusting  on  the  metal  in  contact  with  it.  A  piece  of  iron 
immersed  in  weak  nitric  acid  begins  to  dissolve  at  once.  A  similar 
piece  placed  in  strong  nitric  acid,  touching  it  for  a  few  minutes  with 
a  piece  of  platinum  wire,  and  then  putting  it  into  the  weak  nitric 
acid,  will  not  dissolve,  it  having  been  rendered  passive;  and  simi- 
larly, there  is  reason  why  one  piece  of  iron  may  act  electro-nega- 
tively  toward  another  piece  of  the  same  metal,  on  account  of  some 
slight  alteration  of  its  physical  properties,  by  hammering,  such  as 
closing  the  riveted  seams  of  plates,  calking  seams,  setting  tubes, 
etc.,  or  it  may  have  attached  to  it  some  oxide  of  iron,  which  always 
acts  electro-negatively  toward  any  metal  with  which  it  is  in  contact, 
and  induces  oxidation  in  such  metal." 

The  commission  of  English  engineers,*  appointed  by  the  English 

*  Transactions  Institution  of  Marine  Engineers  (English),  May  13,  1890. 
Minutes  of  Proceedings  Civil  Engineers  (English),  Vol.  LXXVII,  p.  323,  and  Vol. 
LXXXII,  p.  281. 

" Electro-chemical     Effects    on     Magnetizing     Iron."     Proceedings    Royal 


342  CORROSION  OF  METALS  IN  CONTACT. 

Government  to  investigate  the  cause  of  the  failure  of  the  Tay  Bridge, 
reported  that  where  cast  iron  and  wrought  iron  were  connected 
by  rivets  in  many  parts  of  the  same  structure  (as  they  were  in  this 
one),  the  rivets  and  connecting  wrought-iron  work,  where  connected 
to  the  cast-iron  members  of  the  structure  (columns,  flanges,  span- 
drels, etc.),  had  corroded  to  such  an  extent  as  to  be  below  the  point 
of  stability  by  the  local  galvanic  circles  formed  at  numerous  points 
in  the  structure  where  the  two  metals  were  in  contact,  and  the  corro- 
sion thus  established  was  the  cause  of  the  disaster. 

Mr.  St.  John  Day,  in  a  paper  read  before  the  Institution  of  Engi- 
neers and  Shipbuilders,  Scotland,  February,  1880,  stated  that  "  the 
IJ-inch  diameter  bolts  holding  the  ties  to  the  piles  on  the  Tay  Bridge 
were  so  corroded  that  they  would  have  to  be  replaced  every  four  to 
six  years.  Some  of  the  bolts  were  found  to  be  corroded  away  to 
one-half  of  their  o  ginal  size/' 

The  Scotland  Board  of  Trade  now  prohibits  the  connection  of 
cast-iron  columns  with  wrought-iron  columns  or  ties. 

The  corrosive  action  noticed  in  the  riveted  sections  of  the  tubular 
bridge  over  the  St.  Lawrence  River  at  Montreal,  Canada,  referred 
to  before,  resembling  Fig.  39,  Chapter  XXVIII,  was  of  a  similar 
nature  to  the  above  example.  In  this  case,  while  the  corrosion  was 
of  almost  unparalleled  amount  and  virility  in  the  whole  structure, 
the  rivets  that  held  the  floor-beams  and  track-stringers  in  place , 
and  were  under  the  greatest  strain  and  subject  to  vibration  and 
shock  from  the  passing  of  the  railway  trains,  were  corroded  the  most, 
though  all  of  these  parts  were  of  wrought  iron  to  wrought  iron,  but 
varied  in  quality  from  common  iron  to  refined  iron. 

An  important  question  presents  itself  to  boiler-makers:  whether 
it  is  safe  to  rivet  steel  plates  to  iron  plates  in  steam-boilers,  or  even 
in  other  constructions,  particularly  where  exposed  to  high  tempera- 
Society,  Vol.  XIII,  p.  429;  Vol.  XLIV,  p.  152;  Vol.  XLIV,  p.  176;  and  Vol. 
LII,  p.  114. 

"On  the  Corrosion  of  Metals  in  Sea-water."  Minutes  of  Proceedings  Institu- 
tion of  Civil  Engineers  (English),  Vol.  XLXVII,  p.  323,  and  Vol.  LXXII,  p.  281. 

"The  Action  of  Tidal  Streams  on  Metals."  Proceedings  Federated  Institu- 
tion of  Marine  Engineers,  Vol.  I,  p.  191.  1890. 

Report  of  the  meeting  of  the  British  Association  for  the  Advancement  of 
Science,  Edinburgh,  1892. 

"The  Wasting  and  Protection  of  Iron  in  Sea-water." 

From  "Notes  on  Docks  and  Dock  Construction,"  by  C.  Colson,  M.  Inst.  C.E. 

The  Practical  Engineer,  London,  October  19,  1893.     Vol.  X,  No.  399. 


CORROSION  OF  METALS  IN  CONTACT.  343 

tures  or  frequent  changes  of  moderate  temperatures,  or  to  use  iron 
rivets  for  steel  plates  or  steel  rivets  for  iron  plates? 

Cases  are  shown  where  furnace  plates  of  steel  riveted  together 
with  iron  rivets  are  badly  rusted  or  pitted  in  the  vicinity  of  the 
rivets  while  the  latter  remain  intact,.  To  determine  how  iron 
stands  to  steel  and  how  different  amples  of  steel  stand  to  each 
other,  Mr.  Thomson  made  an  extended  series  of  experiments,  using 
a  Thomson's  tangent  galvanometer  to  measure  the  electrical  cur- 
rents generated  in  the  corrosion  of  iron  and  steel,  both  singly  and  in 
connection  with  each  other,  and  when  immersed  in  different  fluids,  viz. : 
sulphuric  acid  (one  part  to  nine  of  water),  caustic-potash  solution 
(specific  gravity,  1.311),  and  chloride-of-ammonium  solution  (specific 
gravity,  1.033),  the  latter  representing  electrically  the  ordinary  con- 
centrated water  found  in  steam-boilers. 

The  details  of  the  experiments  are  important,  but  I  will  give 
only  the  results  obtained,  viz. : 

"  When  an  iron  rivet  and  a  piece  of  the  above-mentioned  corroded 
steel  furnace  plate  were  placed  in  contact  and  immersed  in  the  weak 
sulphuric-acid  bath,  at  first  the  steel  was  electro-negative  to  the 
iron,  but  in  a  few  moments  it  changed,  and  afterward  the  iron  was 
electro-negative  to  the  steel.  When  placed  in  the  chloride-of-ammo- 
nium solution,  at  first  the  iron  was  strongly  electro-positive  to  the 
steel,  and  afterward  became  weakly  electro-negative.  When  placed 
in  the  caustic-potash  solution,  the  steel  was  strongly  electro-positive, 
but  the  current  gradually  became  weaker  and  weaker  until  it  practi- 
cally ceased.  A  new  steel  rivet  in  an  iron  plate,  a  steel  rivet  closed 
by  a  machine  and  held  until  nearly  cold,  an  iron  rivet  closed  on  a  mild 
unworked  steel  plate,  all  reacted  strongly  among  themselves.  The 
iron  when  first  brought  into  voltaic  contact  with  the  steel  was  strongly 
electro-positive  to  the  steel,  being  presumably  strongly  acted  upon 
by  the  solution,  but  after  a  few  minutes  almost  ceased  action  or 
became  reversed;  and  so  far  as  the  tests  demonstrated  as  a  whole, 
it  was  to  the  effect  that  it  was  quite  as  safe  to  bring  iron  and  steel 
in  close  mechanical  contact  with  each  other  as  two  different  kinds 
of  steel  or  two  kinds  of  iron.  Corrosion  was  developed  in  some 
degree  in  the  contact  of  all  different  metals  to  each  other." 

It  is  cited  that  a  number  of  torpedo  boats  of  the  French  Navy, 
that  had  been  constructed  within  ten  years,  and  that  had  not  made  a 
thousand  knots  of  sea  service,  were  found  to  be  so  corroded  at  the 
water-line,  though  well  painted  from  the  first  with  anti-corrosive 


344  CORROSION  OF  METALS.     USE  OF  METALLIC-SALT  PAINTS. 

paints,  they  had  to  be  condemned  for  service;  while  other  boats  of 
the  same  class  that  had  never  been  in  commission,  but  had  been 
laid  up  under  cover,  had,  as  the  report  says,  "eaten  their  own  heads 
off  by  corrosion,"  and  were  condemned  for  the  same  cause.  In  these 
cases  the  corrosion  had  been  in  progress  under  the  paint  covering,  and 
showed  but  little  sign  of  its  extent  or  progress ,  until  the  plates  were 
so  corroded  in  spots ,  many  of  them  of  large  area,  that  the  hammer 
used  in  testing  the  plates  broke  through  the  skin  of  the  boats  under 
the  effect  of  blows  that  would  not  drive  a  nail  into  a  pine  block. 

The  use  of  anti-corrosive  or  anti-fouling  paints,  containing  salts 
of  any  metal,  is  attended  with  the  greatest  danger  to  the  coated 
structure.  These  pigments  are  extremely  sensitive  to  the  presence 
of  saline  elements  in  moisture,  their  action  being  to  rapidly  dissolve 
portions  of  the  iron,  and  to  deposit  the  metal  which  they  contain 
upon  the  surface  of  the  plates,  and  these  deposits  exciting  energetic 
galvanic  action,  cause  corrosion  and  pitting  to  go  on  with  alarming 
rapidity. 

Both  mercury  and  copper  salts  are  offenders  in  this  way,  but 
copper  is  by  far  the  more  objectionable,  from  the  fact  that  the  salts 
formed  by  the  action  of  the  sea-water  upon  the  compounds  used  in 
the  compositions  are  far  more  soluble  than  the  corresponding  salts 
of  mercury,  and  are  therefore  liable  to  be  present  in  much  larger 
quantity,  and  so  exert  comparatively  a  much  more  injurious  action 
on  the  plates. 

As  an  illustration  of  this,  two  equal  portions  of  sea-water  were 
saturated,  the  one  with  copper  chloride,  the  other  with  mercuric 
chloride,  and  into  each  a  piece  of  steel  planed  upon  one  side  and  of 
about  equal  weight  and  size,  was  placed  and  left  for  four  days.  At 
the  end  of  this  period  the  two  plates  were  removed,  and  after  being 
cleaned  and  dried,  were  again  weighed,  when  it  was  found  that  the  one 
exposed  to  the  copper-saturated  sea-water  had  lost  22.2  per  cent  in 
weight,  while  the  plate  exposed  to  the  mercurial  solution  had  only 
lost  3.6  per  cent,  this  being  due  to  the  much  larger  amount  of  the 
copper  salt  soluble  in  the  sea-water. 

On  placing  these  plates  in  clean  sea-water,  corrosion  went  on  in 
each  case  with  extreme  rapidity,  and  after  being  exposed  for  a  month, 
they  had  both  wasted  to  about  the  same  extent ;  that  is  to  say,  when 
once  deposited  on  -the  iron,  mercury  is  practically  as  injurious  as 
copper.  See  further  data  in  Chapter  XXXV. 

In  the  year  1835,  Mr.  Peacock  tried  zinc  plates  on  the  bottom 


CORROSION  OF  METALS.     USE  OF  ZINC.  345 

of  H.M.S.  Medea,  and  in  1867  Mr.  T.  B.  Daft  again  brought  the  sub- 
ject forward,  Sir  Nathaniel  Barnabay,  Mr.  Mclntyre,  and  others 
also  suggesting  various  plans  of  attachment.  In  1888  Mr.  C.  F. 
Kenwood  read  a  paper  before  the  United  Service  Institute,  strongly 
advocating  zinc  sheeting  as  attached  by  his  system. 

When  the  galvanic  contact  was  small,  then  the  sheeting  had  a 
certain  life,  but  afforded  but  little  protection  to  the  iron,  and  gradu- 
ally decayed  away  in  a  very  uneven  fashion;  while  in  those  cases 
where  galvanic  contact  was  successfully  made,  the  ship  on  several 
occasions  returned  from  her  voyage  minus  a  considerable  portion 
of  her  sheeting. 

Another  drawback  to  the  use  of  zinc  sheathing  is  one  which  was 
found  when  it  was  used  to  coat  wooden  ships,  and  that  is  that  sheet 
zinc,  like  every  other  metal,  is  by  no  means  homogeneous,  and  that 
for  this  reason  the  action  of  the  sea- water  upo  it,  leaving  out  of 
consideration  galvanic  action,  is  very  unevenly  carried  on,  the  sheet- 
ing showing  a  strong  tendency  to  be  eaten  away  in  patches,  while 
the  metal  itself  undergoes  some  physical  change  and  rapidly  becomes 
britt  e.  ••,.-• 

Attempts  have  been  made  to  galvanize  the  iron  before  the  building 
of  the  ship,  but  Mr.  Mallett  showed,  in  1843,  that  this  coating  was 
useless  when  exposed  to  sea-water,  as  in  from  two  to  three  months 
the  whole  of  the  zinc  coating  was  converted  into  chloride  and  oxide; 
and  when,  therefore,  galvanizing  is  used  care  must  be  taken  to  pro- 
tect the  thin  coating  of  zinc.  In  any  case  the  galvanizing  must  be 
done  after  the  plates  are  riveted  up,  as  any  break  in  the  surface 
would  set  up  a  rapid  wasting  away  of  the  zinc,  and  the  process  could, 
therefore,  be  only  used  on  small  craft.  Fresh  water  has  less  action 
upon  the  zinc  than  sea-water,  and  for  this  service  galvanizing  would 
be  attended  with  some  measure  of  success,  the  rapid  wasting  of  the 
zinc  in  sea- water  being  due  to  the  salts. 

As  has  been  before  stated,  if  plates  of  iron  or  steel  and  one  of 
copper  be  joined  together  or  placed  in  communication  and  immersed 
in  sea-water,  acidulated  solutions  of  water,  or  of  mineral  salts  or 
oxides,  the  ferric  body  becomes  electro-positive  to  the  copper  and 
is  rapidly  corroded.  The  corroded  metal  is  always  found  in  com- 
munication with  the  positive  pole  or  current  of  electricity,  the  fluid 
soon  becoming  red  from  the  rust  formed. 

In  the  corrosion  of  marine  boilers,  contact  of  different  metals, 
strain,  heat,  and  chemical  action  from  the  sea-water  are  all  present 


346     CORROSION  OF  BOILERS.     USE  OF  ZINC   TO  PREVENT. 

and  acting  towards  the  same  end.  They  are  all  of  different  poten- 
tial and  electro-positive,  and  none  counteract  each  other,  but  all 
attack  the  boiler  metals. 

The  voltage  in  this  case  is  distinctly  recognizable  and  evidently 
much  different  from  the  instances  cited  by  Mr.  Thompson  of  metals 
under  strain  only.  In  one  reported  case,  it  was  one  ohm,  corrosion 
was  marked  and  the  current  grew  stronger  as  the  corrosion  increased. 

Fresh  water  and  solutions  other  than  sea-water,  also  vapors,  are 
corrosive  agents  to  boilers,  the  corrosion  of  which  is  modified,  corrected 
and  rendered  nil,  by  the  use  of  electrogens,  or  heavy  cast-zinc 
plates.  In  old  boilers  using  fresh  or  salt  water,  the  corrosion  in 
progress  is  arrested  by  the  use  of  the  electrogens,  so  long  as  any 
appreciable  amount  of  zinc  is  present.  When  the  zinc  is  wasted 
away  or  removed,  " bleeding"  from  the  boilers  at  once  begins,  par- 
ticularly in  old  boilers  or  in  the  tube  settings. 

In  marine  boilers,  zinc  10"X6"Xl"  to  the  amount  of  one  square 
foot  of  surface  to  50  square  feet  of  heating  surface  is  placed  in  clean, 
firm,  metallic  contact  with  the  internal  steam  or  water  surfaces. 
Too  much  zinc  is  hardly  possible  and  is  better  than  too  little.  The 
amount  of  zinc  can  be  reduced  after  a  time  to  75  or  100  square  feet. 
The  zinc  must  be  placed  in  absolute  contact  with  the  bright  metal 
at  a  number  of  points.  Suspending  the  zinc  in  any  form  in  trays 
or  baskets  will  not  prove  effective.  Zinc  is  slowly  dissolved  in  hot 
water,  and  deposited  as  a  sediment  that  can  be  removed  by  the  blow- 
off,  carrying  with  it  any  old  scale  or  rust  loosened  by  the  galvanic 
action  of  the  zinc.  The  boiler  fluid  contains  a  white  flocculent  pre- 
cipitate of  zinc  (zinc  oxide).  If  the  water  contains  the  sulphates  or 
carbonates  of  lime  or  magnesia,  silicates  or  other  minerals,  that  form 
the  usual  hard,  vitreous  scale,  the  precipitated  zinc  oxide  unites  with 
them  and  holds  them  in  solution  until  blown  out. 

Zinc  causing  old  boilers  to  bleed,  might  be  considered  an  injury 
instead  of  a  blessing.  It  indicates  that  the  boiler  needs  repairs  to 
prevent  future  disasters. 

The  amount  of  zinc  in  boilers  for  land  service  using  waters  con- 
taining mineral  substances,  has  not  been  so  clearly  ascertained  as 
in  the  case  of  marine  work;  but  the  results  in  the  latter  case  are  a 
good  basis  to  reckon  from. 

Any  neutral  salt  in  water  which  decreases  its  resistance,  will 
enable  it  to  act  as  the  necessary  liquid  medium  in  a  voltaic  circuit. 
I,  The  disintegration  of  the  zinc  in  boilers  forms  the  same  oxide 


CORROSION  OF  BOILERS.     USE  OF  ZINC    TO  PREVENT.     347 

that  is  formed  in  the  roasting  furnace  for  pigments,  i.e.,  80.344  parts 
of  zinc  and  19.656  parts  of  oxygen.  The  hydrogen  set  free" replaces 
that  lost  in  the  heating  of  the  water,  that  in  a  measure  is  broken  up 
at  all  heats  below  a  low  red  heat,  where  complete  dissociation  of  the 
hydrogen  occurs.  In  both  the  steam  and  water,  the  flocculent  par- 
ticles of  the  zinc  readily  unite  with  any  ammoniacal,  carbonic,  or  sul- 
phuric acids,  saccharine,  or  other  organic  vapors  or  liquids  present 
to  form  sulphates,  carbonates  of  zinc,  etc.,  that  would  act  mechan- 
ically in  the  water  to  prevent  deposit  and  cause  corrosion. 

Central-heating-system  pipes  develop  a  virulent  corrosion.  The 
reason  for  some  of  the  cases  is  difficult  to  find.  This  corrosion  has 
caused  the  abandonment  of  the  pipes  returning  the  condensed  water 
to  the  boilers,  and  in  some  cases  the  failure  of  the  whole  system. 
The  corrosion  occurs  in  both  the  steam-pipes  and  water-return  pipes, 
being  more  marked  in  the  latter.  In  screwed-end  pipes  the  corro- 
sion first  attacks  the  heel  of  the  pipe  threads  as  zones  of  disintegra- 
tion and  extends  until  the  whole  pipe  is  affected,  though  no  corrosion 
except  at  the  joints  may  be  noticed. 

In  the  steam-pipes  corrosion  takes  the  form  of  pin-holing  or  pitting, 
from  the  inside  at  any  part  of  the  pipe  and  does  not  develop  into  a 
general  corrosion  of  the  surface  as  in  the  case  of  the  hot-water  return 
pipes.  Whenever  a  blow-out  or  pin-hole  from  corrosion  occurs  in 
the  steam  pipe,  a  closing  down  of  the  metal  around  the  hole  by  a 
peen  hammer  stops  the  leak,  which  seldom  reopens.  Peening  the 
metal  has  made  it  more  dense  and  "ess  liable  to  corrode. 

Cast-iron  steam-pipes  are  less  affected  than  wrought-iron  pipes, 
but  the  joints  draw  badly,  owing  to  the  temperature  changes  that 
cause  a  leakage  that  frequent  caulking  only  momentarily  corrects. 
Cement  joints  are  unreliable  under  high  temperatures,  while  rust 
joints  owing  to  their  own  corrosion  burst  the  sockets  of  the  pipes. 

In  central-heating  systems,  the  losses  from  leakage  and  condensa- 
tion amount  to  from  30  to  35  per  cent  yearly,  aside  from  the  loss  of 
the  return  water;  while  the  corrosion  losses  are  about  10  per  cent 
of  the  cost  of  the  pipe  lines. 

Particles  of  dirt,  cinder  in  excess,  unabsorbed  carbon  or  manga- 

"Use  of  Zinc  in  the  Steamship  Hindostan,"  Engineering,  August  7,  1878. 

"The  Corrosion  of  Steamship  Boilers."  The  Practical  Engineer,  Vol.  X, 
Sept^ber  28,  1894. 

"The  Corrosion  of  Boilers."  The  Engineer  (London),  Vol.  LXXVIII,  1894, 
p.  208-281. 


348  CORROSION  IN  CENTRAL  HEATING  SYSTEMS. 

nese  and  impurities  in  the  metal  have  all  been  blamed  for  the  erratic 
disintegration  of  the  pipes,  which  continues  after  many  of  the  above 
causes  have  been  removed. 

In  all  of  these  pipes  a  low  density,  open-grained  filament-formed 
iron,  cinder  in  excess,  heat,  motion  of  vapor  and  water  under  pres- 
sure are  all  present,  and  no  protective  covering  of  moment.  The 
hot  water  is  more  effective  than  steam  in  keeping  the  pipes  clean 
and  bright,  ready  for  corrosive  influences. 

The  disturbance  of  water  by  high  heat  in  being  partially  disso- 
ciated has  been  already  explained  in  this  chapter.  The  action  of 
zinc  on  e'ectrogens,  in  the  case  of  marine  boilers  and  sea-water 
corrosion,  is  always  favorable  for  the  preservation  of  the  metal.  The 
use  of  zinc  to  prevent  corrosion  in  steam-pipes,  radiator  and  heating 
lines,  could  be  hardly  less  favorable. 

M.  Loudin's  (Comptes  Rendus)  experiments  on  the  corrosion  of 
iron  immersed  in  water  usually  found  in  steam-boilers,  was:  That 
with  both  ordinary  and  distilled  water,  the  temperature  had  a  very 
important  influence,  viz. : 

"  At  68°  F.  the  quantities  of  oxygen  absorbed  per  square  foot  of 
iron  surface  per  hour,  when  immersed  in  distilled  water  was  0.258 
grain  and  in  calcareous  water  0.330  grain.  At  212°  F.  the  quantities 
rose  to  2.364  and  2.579  grains.  The  immersion  of  iron  in  water  at  all 
ordinary  temperatures  was  attended  by  the  evolution  of  hydrogen, 
the  action  being  the  least  in  distilled  water.  At  a  temperature  of 
260°  F.,  the  decomposition  of  distilled  water  was  equal  to  the  absorp- 
tion of  0.01  grain  per  square  foot  of  ferric  surface  per  hour,  and  for 
calcareous  water,  0.0129  grain.  For  water  containing  one-fifth  part 
of  crystallized  chloride  of  magnesium,  corrosion  was  0.0182  grain  per 
square  foot,  and  for  water  saturated  with  chloride  of  sodium,  0.05 
grain;  for  sea-water  of  usual  density,  0.067  grain,  all  per  square  foot 
of  iron  surface  per  hour  immersion." 

Corrosion  Increased  by  Stress. 

The  tendency  of  iron  to  change  its  physical  properties  by  a  change 
in  the  condition  under  which  it  may  be  placed  in  ordinary  structural 
work  is  strikingly  shown  by  the  following  instance  taken  from  Engi- 
neering, April  27,  1894,  and  reported  by  Mr.  Oswald  Brown,  M.I.C.E., 
of  32  Victoria  Street,  Westminster. 

"The  cut  (Fig.  51)  shows  portions  of  the  bar  dark  and  corroded, 
while  the  intermediate  layers  have  remained  bright.  The  bands  of 


CORROSION  INCREASED  BY  STRESS. 


349 


rust  extend  over  both  ends  of  the  bar,  giving  it  the  appearance  of 
being  built  up  of  layers  of  two  different  metals.  The  bar,  which  is 
of  the  best  Yorkshire  iron,  gave  under  test  the  following  results : 

" Tensile  strength,  54,230  pounds  per  square  inch;  elongation  on 
8  inches,  28.4  per  cent;  contraction  of  area,  49.6  per  cent.  No  traces 
of  lamination  were  shown  during  the  test,  but  some  months  after,  the 
bar  was  found  in  the  condition  illustrated,  which  shows  that  it  con- 


FIG.  51. — Effect  of  strain  on  the  corrosion  of  iron. 

sists  of  layers  of  different  chemical  composition,  those  which  have 
rusted  being  electro-positive  to  the  other  portions  of  the  bar." 

Iron  rivets  and  iron  plates  in  some  cases  show  the  rivets  corroded 
and  the  plates  unaffected,  and  sometimes  the  contrary,  and  so  with 
steel  rivets  and  steel  plates;  also  iron  rivets  in  steel  plates  or  steel 
rivets  in  iron  plates  all  show  the  most  erratic  evidences  as  regards 
corrosion,  in  many  cases  without  reference  to  the  character  of  the 
water  used  in  the  boiler  or  to  the  external  conditions.  As  a  rule,  all 
analyses  of  the  plates,  rivets,  and  other  material  used  in  boiler  work 
are  made  from  samples  as  they  come  from  the  manufacturer's  hands, 
and  before  being  worked.  Hence,  when  corrosion  of  either  plate 
or  rivet  has  attracted  attention,  it  is  seldom  possible  to  get  a  sam- 
ple of  that  particular  make  and  lot  of  rivets  to  analyze  to  show 
what  physical  changes  were  developed  by  the  processes  of 
heating,  closing  the  rivet,  cold-hammering  the  head,  chipping, 


350  CORROSION  INCREASED  BY  STRESS. 

caulking,  etc.  These  processes,  also  punching  instead  of  drilling 
the  holes,  develop  corrosion,  that  takes  the  form  of  pitting  around  the 
rivets  and  furrowing  on  the  sheet  joints. 

Mr.  Thomas  Andrews,  F.R.S.,  reporting  to  the  British  Institution 
of  Civil  Engineers,  states  his  conclusions  On  the  Effect  of  Stress  on  the 
Corrosion  of  Metals*  In  brief  they  are: 

"That  wrought  iron  and  various  steels,  when  exposed  separately, 
without  liability  to  galvanic  action  other  than  local,  under  the  action 
of  sea-water  for  long  periods,  showed  a  greater  corrosion  on  the  part 
of  all  the  steels  than  the  wrought  iron;  the  advantage  in  favor  of 
the  iron  compared  with  the  steels  amounting  to  25  per  cent  and 
upward.  It  was  also  noticed  that  corrosion  was  increased  in  the 
steels  in  proportion  as  the  percentage  of  combined  carbon  was  greater. 

"  It  was  found  that  the  galvanic  action  between  wrought  iron 
and  steels  induced  a  largely  increased  corrosion  in  both  metals. 
It  was  also  found  that  the  upper  and  lower  portions  of  a  metal  struc- 
ture, or  vessel,  although  composed  throughout  of  the  same  metal, 
were  exposed  to  electrolytic  disintegration  from  the  galvanic  action 
set  up  by  solutions  of  different  salinity  on  the  metal;  conditions 
found  almost  constant  in  tidal  streams,  brought  about  by  the  gradual 
rise  and  inflow  of  salt  water  and  the  outward  flow  of  fresh  water; 
and  there  are  strong  evidences  to  show  that  magnetic  influence  tends 
to  increase  the  corrosion  of  metals. 

"  When,  however,  the  strained  metal  is  in  galvanic  circuit  or  com- 
bination with  the  unstrained  metal  in  any  solution,  an  increased  total 
corrosion  ensues  from  the  galvanic  action,  which  research  has  shown 
to  arise  consequent  on  the  different  potential  between  the  two. 

"  It  was  demonstrated  that  stress  of  any  kind  considerably  alters  the 
physical  properties  of  both  iron  and  steel,  by  increasing  their  rigidity 
and  rendering  the  metals  harder,  also  greatly  reducing  their  prop- 
erties of  elongation  or  ductility.  It  requires  a  higher  tonnage  to  break 
a  strained  than  an  unstrained  bar  of  the  same  metal.  A  tensile  stress 
applied  to  a  wrought-iron  shaft,  that  produces  an  elongation  of  only 
2  per  cent,  increases  the  tensile  resistance  of  the  metal  2.66  per  cent. 

*  Proceedings  of  the  Institution  of  Civil  Engineers  (English),  Vol.  CXYIII, 
1893-94,  Part  IV,  p.  356. 

The  Practical  Engineer  (London),  Vol.  X,  No.  398,  October  12,  1894. 

Iron  Age,  Vol.  No.  17,  October  25,  1894. 

Minutes  of  Proceedings  Institute  Civil  Engineers,  Vol.  LXXXVEI,  p,  340, 
and  Vol.  XCIV,  p.  180;  also  Vol.  CV,  p.  161. 


CORROSION  INCREASED  BY  STRESS.  351 

"From  the  observations  it  was  manifest  that  the  stresses  applied 
to  metals  altered  their  structure,  rendered  them  harder  in  nature, 
and  more  liable  while  in  their  strained  condition  to  be  acted  upon  by 
sea- water,  or  other  waters,  than  in  their  ordinary  normal  or  softer 
condition.  The  experiments,  however,  indicate  that  an  increased 
total  corrosion,  in  excess  of  the  normal  corrosibility  of  the  metal, 
occurs  in  a  metallic  structure,  from  the  action  of  the  local  galvanic 
currents  which  are  shown  to  be  induced  between  strained  and  un- 
strained portions  of  the  same  piece  of  iron  or  steel  forging,  bar,  or 
plate.  Hence  a  strain  occurring  in  a  metallic  structure  tends,  owing 
to  the  local  galvanic  action  thus  set  up,  to  increase  any  corrosive 
forces  which  may  be  deteriorating  the  metal  of  which  it  is  composed." 

The  details  of  the  experiments  are:  Pieces  of  iron  and  mild  steel 
of  known  character  were  submitted  to  tension,  torsion,  and  flexure 
strains,  to  ascertain  the  changes  made  in  the  metal,  and  if  corrosive 
effects  were  in  any  manner  due  to  stress.  For  tension,  a  bar  was 
strained  in  a  testing  machine  until  an  elongation  was  produced  of 
23  per  cent  in  three  inches,  and  at  the  point  of  reduced  area  the  bar 
waj  cut  in  two. 

The  halves  were  then  turned  down  at  the  shackle  or  vise  end, 
where  they  had  been  subjected  to  little  or  no  stress,  until  they  had  an 
area  equal  to  the  end  half  at  the  point  where  contraction  of  area  had 
occurred,  both  pieces  being  finished  exactly  alike  and  each  piece 
represented  a  section  of  strained  and  unstrained  metal.  They  were 
then  placed  at  the  same  depth  in  a  saturated  solution  of  common  salt  to 
approximate  the  action  of  sea-water  on  metal,  the  immersed  ends 
representing  strained  and  unstrained  metal.  An  electrical  contact 
made  between  the  two  pieces  of  metal,  through  the  medium  of  a 
delicate  galvanometer  (Thomson's),  the  difference  in  potential  or 
corrosibility  could  be  observed.  It  was  found  that  in  each  case 
a  sensible  current  was  set  up  between  the  two  halves  of  the  specimen; 
the  strained  portion  was  in  every  case  found  to  be  the  electro-posi- 
tive element  of  the  pair,  corresponding  to  the  zinc  in  a  galvanic 
couple,  indicating  clearly  that  the  strained  metal  was  acted  upon 
more  rapidly  by  the  solution,  and  more  easily  corroded  than  the 
unstrained  metal. 

The  test  made  with  specimens  after  being  submitted  to  torsional 
stress,  representing  a  bar  that  had  been  twisted  through  an  angle  equal 
to  half  a  revolution,  and  prepared  similar  to  those  in  the  tensile  test, 
showed  results  identical  with  the  tensile  strains.  In  every  instance 


352  CORROSION  INCREASED  BY  STRESS. 

the  strained  metal  was  the  electro-positive  element,  and  was  cor- 
roded more  rapidly  by  the  sea-water. 

This  conclusion  was  further  supported  by  tests  made  with  iron 
and  steel  plates,  when  a  flat  piece  was  compared  with  one  bent  into 
an  U  or  semi-circular  trough;  the  bent  plate  in  each  case  proving 
to  be  the  one  most  easily  acted  upon  by  the  solution. 

The  experiments  throw  an  interesting  light  on  a  subject  which 
has  hardly  received  the  attention  it  deserves,  and  helps  to  explain 
some  of  the  peculiarities  in  connection  with  the  wasting  of  certain 
structures  that  have  been  involved  in  considerable  mystery.  The 
metals  operated  upon  by  Mr.  Andrews  were  large,  rolled  wrought- 
iron  bars  and  hammered  wrought-iron  shafts;  Bessemer  steel  and 
Siemens  steel  forged  shafts,  also  arge  bars  of  soft  and  hard  Bessemer 
and  Siemens  steel;  soft  and  hard  cast  steel,  and  steels  made  from 
each  of  the  metals  aluminum,  nickel,  silicon,  and  copper.  Experi- 
ments were  also  made  on  rolled  plates  of  wrought  iron,  soft  Bessemer 
and  soft  and  hard  Siemens  steel  and  soft  cast  iron.  The  chemical 
compositions  and  general  physical  properties,  etc.,  of  all  the  metals 
are  given  and  tabulated.  All  the  metals  experimented  upon  were 
perfectly  bright. 

General  results:  The  average  electromotive  force  obtained  be- 
tween strained  and  unstrained  portions  of  the  same  metal  were,  viz. : 

Wrought-iron  forged  shafts 0 . 016  volts. 

Soft  Bessemer  steel  forged 0.019  " 

Hard        "  "        "      0.006  " 

Soft  cast  steel 0.003  " 

Hard    "       "    0.003  " 

Silicon  steel '. 0.004  " 

Aluminum  steel 0 . 004  " 

Nickel  steel 0 . 003  " 

Rolled  wrought-iron  bars 0 . 002  " 

Soft  Siemens  steel 0 . 005  " 

Hard      "  "    0.005  " 

Copper  steel 0.006  " 

Chromium  steel 0".  001  " 

Bessemer  steel  hammered  forgings 0.011  " 

Siemens  steel  "  "       0 . 006  " 

With  cold-drawn  small  steel  rods  in  galvanic  circuit  with  copper 
rods,  similar  results  were  noted,  the  electromotive  force  between 
strained  and  unstrained  aluminum  steel  being  0.022  volts,  and 
strained  and  unstrained  cast  steel  being  0.023  volts. 


CORROSION  INCREASED  BY  STRESS. 


353 


In  all  these  tests  the  strained  metal  was  the  electro-positive. 
In  the  torsional  tests  the  electromotive  force  was  notably  higher 
than  in  the  tensile,  also  in  the  flexure,  tests. 

These  electric  measurements  ought,  perhaps,  to  be  regarded  as 
tentative  indications,  establishing  a  general  principle,  rather  than 
as  an  absolute  measurement  for  the  purpose  of  accurate  comparison 
of  the  behavior  of  the  various  metals.  The  chemical  analysis  of 
all  the  metals  was  made  prior  to  straining  them.  These  experiments 
extended  from  a  few  seconds  to  over  ten  days,  in  which  it  was  ob- 
served that  the  difference  in  the  electromotive  force  between 
strained  and  unstrained  metal  steadily  declined  from  the  initial 
amount,  but  was  in  no  case  extinguished. 

Corrosion,  or  the  oxidation  of  substances  by  chemical  action  is 
always  accompanied  by  electrical  energy,  that  may  be  of  more  or  less 
intensity ,  or  electromotive  force  according  to  the  substance  con- 
sumed. 

Chemical  action  is  probably  due  to  the  unbalanced  attraction 
among  the  various  molecules  of  matter  lying  in  juxtaposition,  the 
rearrangement  of  which  caused  by  strain  or  a  change  in  the  thermal 
or  electrical  conditions  of  one  atom  changes  them  all.  It  is  known 
that  a  change  in  either  the  thermal  or  electrical  conditions  develops 
corrosion  in  certain  circumstances  but  does  not  in  many  other  cases 
of  apparently  the  same  nature.  The  amount  of  electromotive  force 
developed  in  the  oxidation  of  a  few  substances  is  indicated  in  the  fol- 
owing  instances :  * 


Substances. 

Heat  of  Oxidation  of 
Equivalent. 
Calories.     B.  T.  Units. 

E.M.F.  Relative 
to  Oxygen. 

E.M.F.  Relative 
to  Zinc. 

Carbon     

2,000  =     7,938 

0   09 

—  1    74 

Silver     

9,000=  31,742 

0  39 

—  1   44 

Copper.  . 

18,760=  74,057 

0  80 

—  1  08 

T    FV 
.Lead  „  

25,100=  99,616 

1  12 

—0  71 

Iron  

34,120  =  135,415 

1  55 

—0  28 

Zinc  
Peroxide  of  lead  

42,700  =  169,074 
12,500=  48,022 

1.83 
0.52 

0.00 
-2.35 

The  corrosion  of  ferric  bodies  results  from  the  decomposition 
of  water  or  air  by  electrical  energy. 

As  detailed  in  Chapter  III,  atmospheric  moisture  in  the  presence 
of  iron  at  a  temperature  of  900°  F.  releases  oxygen  and  forms  the 


*  Thompson's  Electricity  and  Magnetism. 


354    CORROSION  OF  METAL.    ELECTRO-CHEMICAL  ACTION. 

black  magnetic  or  stable  oxide  of  iron,  that  in  manufactured  articles 
is  represented  by  the  Bower-Barff  products. 

Every  pound  of  iron  oxide  represents  the  energy  of  1.668  pound 
of  coal  required  for  its  formation.  This  rust  requires  .3375  pound 
6f  water  to  furnish  the  necessary  oxygen.  A  pound  of  iron  oxide 
represents  the  corrosion  of  13.13  square  feet  of  metallic  iron  ToV?r  inch 
in  thickness  and  has  developed  163,233  B.  T.  Units  (.0641  H.P.), 


Zn.       Pb»       So.       E&,      $b.       Cib       CcL 

FIG.  52. — Diagram  of  the  corrosibility  of  metals. 

or  equal  to  an  electromotive  force  of  1.55,  to  neutralize  which  would 
require  the  oxidation  of  .847  pound  of  zinc. 

In  all  of  these  oxidations  the  thermal  manifestations  are  subordi- 
nate, and,  with  the  electrical  energy  being  of  low  potential,  when  they 
extend  over  any  considerable  period,  are  unrecognized  or  difficult  to 
determine. 

The  affinity  of  oxygen  for  hydrogen  represents  an  electromotive 
force  of  1.47  volt.  The  decomposition  of  water  acidulated  by  sul- 
phuric acid  yields  at  the  cathode  11.12  parts  of  hydrogen  and  at  the 
anode  88.18  parts  of  oxygen;  about  1  per  cent  of  ozone  being  formed 
from  the  oxygen. 

The  decomposition  of  1  pound  of  zinc  for  the  protection  from 
corrosion  of  marine  boilers  or  other  like  ferric  bodies  evolves  9840  cubic 
inches  of  hydrogen,  equal  to  5.694  cubic  feet,  that  weighs  210.29 
grains,  or  .3329  pound. 

The  late  Henry  Morton,  Ph.D.,*  stated  that  a  pound  of  zinc  con- 
sumed in  the  following-named  batteries  develops: 

*  "The  Maximum  Possible  Efficiency  of  Galvanic  Batteries."  Cassier's 
Magazine,  June,  1895,  p.  130. 


CORROSION  OF  METAL.     ELECTRO-CHEMICAL  ACTION.      355 


B.  T.  Units. 

Horse-power. 

Smee's  battery                            .  .        

900 

0  35 

Daniels  's  (sulphate  of  copper)  battery  

1419 

0  55 

Grove's  or  Bunsen's  (nitric  acid.)       '* 

2722  4 

1  06 

Pegffendorf's  (chromic  acid)              " 

2827  5 

1   14 

Sulphuric  acid  (1  in  9  parts  of  water)  

3006 

1.17 

All  losses  from  resistance  being  excluded. 

A  series  of  experiments  covering  several  years,  upon  the  corrosi- 
bility  of  metals,  has  been  made  at  the  University  of  Wisconsin,  under 
the  supervision  of  Prof.  Dugald  C.  Jackson. 

Prof.  Jackson,  in  the  discussion  of  paper  No.  901,  "Protection 
of  Ferric  Structures,"  *  referred  to  the  results  of  his  experiments, 
from  which  I  briefly  quote:  "When  a  piece  of  iron  or  steel  is  placed 
in  a  testing  machine  and  its  electrical  condition  is  followed  up  during 
the  straining  test,  its  corrosibility  appears  to  increase  practically  in 
proportion  with  the  strain,  so  that  a  diagram  plotted  with  stress  along 
one  coordinate  and  corrosibility  along  the  other  appears  to  be  of 
almost  exactly  similar  character  to  a  diagram  plotted  with  stress 
and  strain  along  the  two  axes  of  coordinates. 

"  Two  illustrations  of  these  diagrams  are  presented,  Figs.  53  and 
54,  from  test  pieces  of  wrought  iron 

"  In  the  case  of  cast  iron  Fig.  55  shows  the  stress-corrosibility 
diagrams  for  two  specimens  in  tension.  A  comparison  of  these  dia- 
grams with  those  for  wrought  iron  in  tension,  illustrated  in  Figs.  53 
and  54,  shows  the  marked  difference  between  the  two  metals.  Fig.  56 
shows  a  stress-corrosibility  diagram  for  cast  iron  in  compression. 
The  exact  forms  of  the  diagrams  taken  from  cast  iron  depend  in  some 
degree  on  the  physical  character  of  the  specimens,  but  the  diagrams 
shown  are  typical  ones.  The  effect  of  strain  is  small  in  the  case  of  cast 
iron. 

"  The  corrosibility  of  the  specimens  was  measured  by  determining 
the  electromotive  forces  of  the  test  pieces  toward  a  standard  electrode 
in  a  normal  solution. 

"The  results  of  the  tests  show  that  in  bridge  members  and 
similar  pieces  that  have  been  worked,  the  metal  appears  to  be  easily 
affected  by  corrosion,  this  corrosion  being  properly  characterized  as 


*  Transactions  American  Society  Mechanical  Engineers,  Vol    XXII    Paper 
No.  901,  May,  1901. 


356 


STRESS-CORROSION  DIAGRAMS. 


15000 
10000 


15000 

10000 

5000 

0 


WROUGHT  IRON  (%5  DIAMETER) 


FIG.  53. — Stress-strain  and  stress  corrosibility  of  wrought  iron. 


HT  IRON  (^DIAMETER) 


15000 


10000  -g 


FIG.  54. — Comparison  of  stress-strain  and  stress-corrosibility  diagrams,  wrought 

iron. 


STRESS-CORROSION  DIAGRAMS. 


357 


caused  by  electrolysis  ;   that  is,  the  strained  metal  is  really  eaten 
away  and  the  unstrained  metal  is  not. 

"  The  experiments  give  a  satisfactory  explanation  of  much  of  the 
so-called  grooving  in  boilers  and  corrosion  of  a  similar  character.  Here 
the  strained  metal  of  a  punched  boiler  plate  that  is  not  completely 
covered  by  a  rivet-head  becomes  eaten  away.  Or  perhaps  a  plate 
becomes  strained  at  a  joint  by  temperature  stresses  and  the  strained 


20000 


10000 


13000 


4000 


20000 


1(5000 


12000 


4000 


r 


-0.0590  -0.0582  -0.0574 

Corroslbility  in  arbitrary  units. 


-0.0600  -0.0592  -0.0584  -O.Q57G 

Corrosibllity  In  arbitrary  units. 


FIG.  55. — Stress-corrosibility  diagrams  for  cast  iron. 

streak  is  corroded.  In  each  case  the  strained  metal  is  of  greater  corrosi- 
bility,  and  it  acts  as  one  of  the  plates  of  an  electric  battery  in  which 
the  other  plate  of  the  battery  is  the  unstrained  metal  of  the  boiler 
shell,  and  the  electrolyte  is  the  water  within  the  boiler.  The  strained 
metal  is  the  electrode  which  corresponds  to  the  zinc  of  the  ordinary 
voltaic  cell,  and  it  is  eaten  away. 

"  Another  illustration  of  corrosion  of  this  character  is  the  so-called 
(by  bridge  engineers)  Cooper's  lines,  which  are  often  evidenced  in 
the  corrosion  of  bridge  members.  These  are  lines  of  electrolytic 
corrosion  in  strained  parts.  The  most  seriously  strained  parts,  or 
parts  that  have  become  hardened  in  working,  are  eaten  away 
by  voltaic  action,  which  goes  on  at  their  expense,  and  the  less  strained 


358 


STRESS-CORROSION  DIAGRAMS. 


100000 


60000 


40000 


20000 


T 


-0.027  -0.019  -0.011 

Corrosibility  In  arbitrajqy  units* 

.  56. — Stress-corrosibiiity  diagram  of  cast  iron  in  compression. 


40000 


24000 


16000 


7 


f 


-0.589  -0.588  -0.587  -0.586  -0.585 

Corrosibility  in  arbitrary  units* 

FIG.  57. — Stress-corrosibiiity  diagram  of  hard-drawn  copper  wire. 


HAMBUCHEN'S  EXPERIMENTS  IN  RAPID   CORROSION.     359 

parts  are  less  rapidly  corroded,  thus  leaving  the  appearance  of  lines 
of  corrosion. 

"It  is  also  true  that  metals  which  do  not  change  their  physical 
characteristics  when  strained,  apparently  do  not  materially  change 
in  corrosibility  as  the  result  of  strain.  Thus  if  lead  is  stretched,  its 
corrosibility  does  not  appreciably  increase.  The  same  is  true  to  a 
certain  degree  of  brass  and  copper.  Fig.  54  represents  a  stress- 
corrosibility  diagram  for  hard-drawn  copper.  The  same  is  true  also, 
to  a  limited  degree,  of  very  soft  iron,  but  as  even  the  softest  iron 
does  harden  so  we  what  when  strained,  its  corrosibility  is  somewhat 
affected  by  strain." 

An  experimental  study  of  the  corrosion  of  iron  and  steel  under 
different  conditions  has  been  made  by  Mr.  Carl  Hambuchen,  B.Sc.* 
These  experiments  were  conducted  on  the  lines  of  those  of  Mr.  Thomas 
Andrews,  F.R.S.,  hereinbefore  given,  "on  the  effect  of  strain  on  the 
corrosibility  of  metal." 

Hambuchen's  apparatus  and  method  of  testing,  and  the  checks 
and  precautions  against  errors,  especially  in  obtaining  the  value  of 
the  electromotive  force,  were  superior  to  those  heretofore  employed 
by  experimenters,  and  the  results  are  more  in  accordance  with  the 
practical  experience  of  the  present  day. 

A  hindrance  to  experimental  investigation  of  the  corrosion  of  metal 
is  the  length  of  time  required  to  produce  measurable  results.  Ham- 
buchen took  advantage  of  the  fact  that  corrosion  being  developed 
by  an  electric  current  flowing  from  the  ferric  body  to  the  electrolyte, 
the  rate  of  corrosion  could  be  greatly  increased  by  causing  a  current 
generated  externally  to  flow  from  the  metal  as  an  anode,  thus  causing 
the  corrosion  to  occur  under  what  may  be  termed  exaggerated  or 
intense  conditions,  the  metal  being  corroded  as  much  in  a  few  hours 
as  it  would  be  in  as  many  years  by  exposure  to  the  weather;  the 
resultants  being  practically  the  same  as  the  effects  produced  by 
ordinary  corrosion. 

The  losses  in  weight  from  corrosion  in  different  irons,  steels,  and 
other  metals,  under  strain,  from  nil  to  breakage,  are  tabulated,  also 
the  loss  in  weight  of  metal  per  ampere  hour,  and  the  electromotive 
force  developed  at  various  points  of  the  strain. 

Normal  solutions   of  ammonium  chloride,   ammonium  sulphate, 

*  Excerpts  from  Bulletin  of  the  University  of  Wisconsin,  No.  2,  Engineering 
Series.  Vol.  II,  No.  8,  July,  1900.  Illustrated. 


360     HAMBUCHEN'S  EXPERIMENTS  IN  RAPID   CORROSION. 

potassium  nitrate,  sulphate  and  chlorides  of  nitre,  were  used  for  the 
electrolyte.  The  experiments  determined  that  the  loss  in  weight  of 
the  metal  in  the  different  solutions  was  practically  the  same,  and  that 
whether  the  salts  were  sulphates,  nitrates,  or  chlorides  did  not  materi- 
ally affect  the  rate  of  corrosion.  The  ampere  hours  varied  from  11 
to  13.6  and  the  exposures  from  19.5  to  24.25  hours. 

Interesting  facts  were  developed  showing  the  variable  nature 
of  " pitting"  in  mild  steel  exposed  to  different  solutions.  Figs.  58 
and  61  show  a  round  pitting'  as  the  result  of  the  ammonium  chloride  ; 
an  elongated  pitting  results  from  the  ammonium  sulphate,  and  a 
more  uniform  corrosion  from  a  potassium-nitrate  solution.  In  the 
cast-iron  specimens,  Fig.  59,  the  corrosion  consisted  of  a  soft  carbona- 
ceous material,  which  generally  adhered  very  firmly  to  the  surface 
of  the  iron.  In  case  the  current  density  was  carried  beyond  0.025 
amperes  per  square  inch,  this  soft  material  would  separate  from  the 
iron  after  attaining  a  certain  thickness.  The  formation  of  this  layer 
must  offer  some  resistance  to  the  flow  of  the  current,  and  therefore 
protects  it  to  a  certain  degree.  Or,  in  other  words,  a  given  potential 
difference  between  an  iron  pipe  and  a  railway  track  would  cause  less 
flow  if  the  pipe  thus  coated  were  cast  iron,  than  if  it  were  wrought 
iron,  which  would  quickly  reveal  its  weakness  by  the  different  char- 
acter of  the  corroded  coating.  But  with  a  given  amount  of  current 
flowing  from  normal  cast  iron  and  wrought  iron,  the  corrosion  is 
nearly  equal  in  amount  in  the  two. 

It  was  noticed  in  the  case  of  the  cast-iron  anodes  that  there  was 
a  liberation  of  gas  during  the  process  of  corrosion.  That  this  was 
not  due  to  the  flow  of  the  current  was  shown  by  interrupting  the 
current,  the  liberation  of  the  gas  continuing  for  some  time  after. 
The  nature  of  the  gas  was  not  determined,  nor  of  what  the  action 
consisted. 

If  the  current  density  was  not  excessive,  the  iron  did  not  undergo 
any  material  change  in  appearance,  even  though  subjected  to  the 
action  of  the  current  for  a  long  time.  But  although  the  general  form 
and  outward  appearance  of  the  cast  iron  remained  the  same,  the 
fact  that  its  structure  had  been  materially  altered  was  shown  by 
cutting  it.  The  cast  iron  was  found  to  be  softened  to  a  certain 
depth,  the  material  removed  having  the  appearance  of  fine  iron 
filings  and  graphite,  making  the  loss  to  the  iron  equal  to  1.17  grains 
per  ampere  hour  for  10.72  square  inches  of  exposed  area.  This 
coating  if  allowed  to  stand  until  dry  became  much  harder  and  offered 
some  resistance  to  cutting;  but  the  iron  had  lost  its  original  strength. 


HAMBUCHEN'S  EXPERIMENTS  IN  RAPID  CORROSION.    361 

The  effect  of  the  presence  of  mill-scale  on  the  rapidity  of  corro- 
sion is  shown  by  Figs.  58-61  and  65  in  comparison  with  the  polished 
plates  of  the  same  metal. 

Changing  the  crystalline  structure  of  steel  by  annealing,  hardening, 
and  burning,  causes  the  amount  of  corrosion  to  vary,  as  is  noted  in 
the  tables  on  pages  363-364.  The  amount  of  corrosion  per  ampere 
hour  of  the  hardened  steel  is  considerably  less  than  that  of  the 
annealed  or  burned  steel. 

This  is  an  apparent  discrepancy  with  other  data  and  observa- 
tions in  regard  to  strained  metal  being  the  most  subject  to  corro- 
sion. Hardened  steel,  being  necessarily  under  a  highly  strained 
condition,  should  have  shown  greater  corrosibility  than  the  annealed 
or  burned  specimens.  That  it  did  not  is  owing  to  the  fact  that  the 
high  tension  between  the  particles  held  them  in  place  until  they 
were  severally  corroded  entirely  away.  In  the  burned  or  annealed 
steel  the  particles,  when  only  partially  corroded,  were  loosened  in 
their  bond  to  each  other,  and  cast  from  the  mass  before  being  entirely 
corroded.  The  pitting  of  the  annealed  steel,  Fig.  66,  the  composi- 
tion of  which  is  similar  to  that  of  sheet  iron,  Fig.  72,  shows  a  greater 
corrosibility  than  the  hardened  steel,  due  to  the  above  reason. 

The  small  percentage  of  carbon  and  other  impurities  in  the  steel 
would  not  account  for  the  corrugations  in  the  burned  and  hardened 
steel,  shown  by  the  figures.  It  would  be  unreasonable  to  suppose 
that  the  impurities  or  carbon  could  be  regularly  distributed  as  indi- 
cated by  the  corrugations ;  they  must  be  due  to  lines  of  strain  in  the 
metal  that  corrosion  developed. 

The  metals  that  are  electro-positive  to  iron  and  steel  are  magne- 
sium, aluminum,  zinc,  and  cadmium ;  while  lead,  antimony,  tin,  copper, 
silver,  carbon,  manganese,  and  some  of  the  metallic  oxides,  are 
electro-negative  to  ferric  bodies. 

Test  plates  of  clean,  bright  wrought  iron,  cast  iron,  and  steel 
were  drilled  and  the  several  holes  plugged  with  one  of  the  above 
metals.  The  plates  were  then  placed  in  sand  saturated  with  ammo- 
nium chloride  and  other  corrosive  solutions,  and  after  a  short  expo- 
sure were  examined ;  all  the  plates  in  which  the  electro-positive  metal 
plugs  were  placed  were  found  clean  and  bright,  while  the  plugs  were 
more  or  less  corroded.  In  the  other  set  of  plates  the  surfaces  were 
corroded  while  the  plugs  were  not  affected.  In  the  plates  fitted 
with  the  zinc  and  other  electro-positive  metals,  the  current  flowed 
from  the  solution  to  the  plates  and  corrosion  did  not  take  place. 


362    HAMBUCHEN'S  EXPERIMENTS  IN  RAPID    CORROSION. 

In  the  plates  with  the  lead,  carbon,  and  other  electro-negative  sub- 
stances, the  current  flowed  from  the  plates  to  the  solution  and  the 
plates  were  corroded. 

The  conditions  of  electrolytic  corrosion  apply  to  most  of  the 
metallic  oxides  as  well  as  to  the  metals,  and  are  developed  in  both: 
1.  When  two  or  more  conducting  substances  are  in  contact  with  an 
electrolyte.  2.  Whenever  there  is  any  difference  of  electrical  poten- 
tial between  such  bodies.  3.  When  a.  suitable  connection  between  the 
conducting  substances  furnishes  a  path  for  the  flow  of  the  current. 

All  of  these  conditions  are  present  in  the  decay  of  paint  coatings 
as  well  as  the  corrosion  of  iron  and  steel.  The  electrolyte  consists  of 
moisture  in  any  form,  and  may  be  acidulated,  saline,  or  fresh. 

Iron  and  steel  rea  never  pure  or  homogeneous;  they  contain 
upon  their  surfaces  many  substances,  such  as  carbon,  graphite,  mill- 
scale,  and  particles  of  metal  and  oxides.  The  body  of  the  metal 
may  be  formed  from  scrap  iron  of  different  natures,  and  the  heat 
of  fusion  seldom  renders  the  mass  homogeneous. 

In  cast  iron  and  steel,  in  their  many  processes  of  manufacture,  there 
are  many  irregular  zones  of  density  and  purity  each  of  which  has  its  own 
potential.  Between  all  of  these  differently  charged  bodies  a  current  of 
electricity  is  set  up,  the  circuit  being  completed  through  the  electrolyte. 

This  electric  current  flowing  from  the  metal  to  the  electrolyte 
will  cause  corrosion  of  the  metal,  which  may  be  general  over  the 
whole  surface  of  it,  or  be  localized  in  spots,  according  to  its  composi- 
tion, which  is  affected  by  local  disturbances,  such  as  welds,  strains, 
annealing,  burning,  and  hardening,  or  the  presence  of  foreign  sub- 
stances. Some  peculiar  cases  of  corrosion  can  be  explained  by  ascer- 
taining if  the  metal  has  been  subjected  to  some  of  these  influences, 
that  otherwise  would  be  classed  as  mysterious. 

Mr.  Hambuchen,  in  order  to  draw  a  comparison  between  electro- 
lytic corrosion  and  ordinary  corrosion,  immersed  specimens  similar 
to  those  exposed  to  electrolytic  action  in  a  tank  containing  a  normal 
solution  of  ammonium  chloride,  and  left  them  undisturbed  for  four 
months.  The  results  obtained  showed  that  the  amount  and  character 
of  corrosion  depend  upon  the  quality  of  the  metal,  and  confirmed  the 
conclusion  derived  from  electrolytic  corrosion.  The  time  of  exposure  of 
these  specimens  was,  however,  too  short  to  develop  any  marked  pittings 
or  other  corrosive  effects  shown  so  plainly  in  the  electrolytic  samples. 

Some  of  the  conclusions  given  by  Mr.  Hambuchen  as  the  result 
of  his  tests  are: 


HAMBUCHEN'S  EXPERIMENTS  IN  RAPID  CORROSION.    363 


That  electrolytic  corrosion  produced  by  the  flow  of  a  current  of 
moderate  density  from  an  external  source,  produces  results  on  the 
metal  which  are  similar  to  those  produced  by  corrosion  under  ordinary 
conditions. 

In  many  if  not  all  cases  the  character  and  rapidity  of  ordinary 
corrosion  of  iron  and  steel  depend  upon  their  physical  and  chemical 
properties,  and  the  galvanic  action  due  to  differences  in  potent  al 
between  different  parts  of  the  metal. 

The  application  of  stress  to  metals  causes  an  increase  in  chemical 
activity,  this  increase  being  especially  marked  after  the  elastic  limit 
is  reached. 

It  is  possible  to  plot  a  curve  showing  the  relation  of  electromotive 
force  to  strain,  which  is  similar  to  that  of  stress  to  strain. 

There  is  a  definite  relation  between  the  electrical  potential  of 
any  metal  toward  an  electrolyte  and  the  amount  of  energy  stored  up 
in  the,  metal  through  the  application  of  stress.  It  is  evident  that  the 
protection  of  ferric  structures  from  corrosion  requires  their  removal 
from  electrolytic  influences. 

The  several  specimens  subjected  to  different  conditions  of  corro- 
sion were  all  taken  from  the  same  bar  or  sheet  to  facilitate  comparison. 

The  following  tables  are  means  of  a  few  of  the  separate  results 
given  by  Mr.  Hambuchen: 

Table  showing  the  loss  in  weight  of  iron  and  steel  used  as  anodes,  immersed'  in 
a  solution  of  ammonium  chloride  and  exposed  to  the  action  of  an  electric  current 
of  varying  densities  and  time. 


Material  and  Condition  of  Surface. 

Area  in 
Square 
Inches. 

Total  Loss 
in  Weight. 
Grams. 

Weight 
Lost   per 
Ampere 
Hour. 
Grams. 

Ampere 
Hours. 

Ex- 
posure 
Hours. 

Annealed  steel   polished 

10 

15  9 

1    1683 

13   6 

233 

"           "      with  scale 

10  523 

15  33 

1  1163 

13   3 

194 

Hardened  steel  polished 

10 

14  633 

1  077 

13  6 

23? 

"            "      with  scale 

10  48 

14  407 

1  059 

13  3 

^o4 
19  5 

Steel  burned,  not  hardened  or  pol- 
ished                      

10. 

15.666 

1.1526 

13.6 

23| 

Steel  burned,  not  hardened  with  scale 
Steel  burned,  hardened,  and  polished 
Cast  iron  polished        

10.3 
10.555 
10.073 

15.515 

12.875 
12.273 

1.1575 
1  .  1475 
1  .  0983 

13.3 
11.2 
11.2 

19| 

24i 
241 

"      "     scale  partly  removed  

10.693 

9.996 

0  .  7506 

13.3 

19i 

Sheet  iron  polished     

10.373 

13.87 

1.184 

11.2 

241 

"       "     scale  partly  removed.  .  .  . 

10.263 

14.63 

1.084 

13.3 

19J 

It  will  be  noticed  that  the  amount  of  corrosion  for  all  of  the  specimens  is 
greater  per  ampere  hour  than  the  theoretical  amount  given  by  Faraday's  law 
(1.0448 -grains  per  square  foot  of  surface  per  ampere  hour),  cast  iron  with  the 
scale  partly  removed  being  an  exception. 


364 


HAMBUCHEN'S  FIGURES  OF  CORROSION. 


Table  showing  the  loss  in  weight  of  iron  and  steel  exposed  to  corrosion  by 
immersion  for  4  months  in  a  solution  of  ammonium  chloride. 


Metal  and  Condition. 

Area  in 
Square 
Inches. 

Total  Loss 
in  Weight. 
Grams. 

Loss  in 
Weight  per 
Square  Inch. 
Grams. 

10  437 

0  733 

0  066 

"       "     scale  partly  removed  

10  30 

473 

0  142 

"       "     with  scale                                . 

10  556 

793 

1  698 

Cast  iron  surface  polished                   .    . 

13  596 

083 

0  0793 

"       "     scale  partly  removed 

14  16 

663 

0  117 

"       "     with  scale                             .    . 

14  117 

663 

0  1174 

Annealed  steel  surface  polished         ... 

10  37 

0  733 

0  0708 

"            "     scale  partly  removed.  . 

10  603 

1  08 

0  102 

"            "     with  scale              

10  336 

2  00 

0  193 

Hardened  steel  with  scale     

10  57 

1  063 

0  9985 

Steel  with  scale  burned  not  hardened.  .  .  . 

10  255 

3  70 

0  3613 

FIG.  58. — Mild  steel  (ammonium-chloride  solution).     Magnified  2$  diameters. 


FIG.  59.— Cast  iron  (polished).     Magnified  2|  diameters. 


HAMBUCHEN'S  FIGURES  OF  CORROSION. 


365 


FIG.  60. — Cast  iron  (with  scale).     Magnified  2-|  diameters. 


FIG.  61. — Mild  steel  (ammonium- chloride  solution).     Magnified  2£  diameters. 


FIG.  62. — Burned  and  hardened  steel.     Magnified  2£  diameters. 


366  HAMBUCHEN'S  FIGURES  OF  CORROSION. 


FIG.  63. — Burned  steel  not  hardened  (with  scale).     Magnified  2|  diameters. 


FIG.  64. — Annealed  steel  (polished).     Magnified  2$  diameters. 


FIG.  65. — Annealed  steel  (with  scale).     Magnified  2|  diameters. 


HAMBUCHEN'S  FIGURES   OF  CORROSION. 


367 


FIG.  66. — Steel  burned  but  not  hardened  (polished).     Magnified  2£  diameters. 


FIG.  67. — Hardened  steel  (polished).     Magnified  2|  diameters 


FIG.  68. — Hardened  steel  (with  scale).     Magnified  2|  diameters. 


368 


HAMBUCHEN'S  FIGURES  OF  CORROSION. 


FIG.  69. — Steel  burned  and  hardened  (polished).     Magnified  2|  diameters. 


IFlG.  70. — Sheet  iron  (polished).     Magnified  2£  diameters. 


<V**>V'l  • "  *       .  "%    -.  "'-T*  '  ^  '  x*i^ 

-»^    ^r*x*v;;^Z    ^...i*  .^v  *%fe  J^^r^^*^ ' 

:i^^??:c%^"1  '^V^SSv 
S^S™fc3fr  ^  I  v  •  ?^*'^f  *  . 

^^\;^^v^^^>^^ 

rf^^iZ^iL^  Htifc.-..'*?     ?A»^^l5 


FIG.  71.— Sheet  iron.     Magnified  2£  diameters. 


HAMBUCHEN'S  FIGURES  OF  CORROSION.  369 


FIG.  72. — Sheet  iron  (with  scale).     Magnified  2£  diameters 


CHAPTER  XXXIV. 

ELECTROLYSIS   OF   UNDERGROUND   METAL. 

PROF.  EDWIN  J.  HOUSTON  defines  electrolysis  as  chemical 
decomposition  effected  by  means  of  an  electric  current;  that  is, 
the  source  of  electrolytic  corrosioa  lies  in  the  release  of  an  atom  of 
oxygen  from  any  moisture  and  its  instantaneous  combination  with 
any  iron  it  can  seize  upon." 

Prof.  D.  C.  Jackson  (University  of  Wisconsin)  defines  its  action: 
"In  an  electrolytic  cell  with  iron  electrodes,  having  any  salt  or  salts 
of  alkaline  metals  or  earths  in  solution  in  the  electrolyte,  the  salts  are 
decomposed,  their  acid  radicals  attacking  the  anode,  forming  an 
iron  salt. 

A  proof  of  this  theory  is  found  in  the  storage  battery,  in  the  charg- 
ing of  which  a  large  current  is  discharged  from  a  lead  plate  into  an 
electrolyte  consisting  of  dilute  sulphuric  acid.  In  a  storage  battery 
the  oxidation  of  both  plates  takes  place  but  the  red  oxide  of  lead 
formed  is  very  different  in  character  from  the  corrosive  effects  of  an 
electric  current  on  an  underground  lead-pipe." 

*  "There  is  nothing  mysterious  about  the  corrosion  of  metals  b}' 
electrical  currents.  Its  action  is  precisely  similar  to  that  employed 
by  electro-platers  in  their  art.  Two  plates  of  metal  placed  in  any 
material,  whether  damp  earth  or  the  solution  vat  of  an  electro- 
plating apparatus,  a  current  of  electrical  energy  will  be  instituted 
from  one  plate  to  another  and  the  plate  or  object  from  which  the 
current  flows  will  be  corroded.  The  current  will  make  its  own  selec- 
tion as  to  its  course  and  the  body  to  be  attacked.  In  the  case  of 
metals  buried  in  earth  or  water,  the  electrolytic  action  is  out  of  sight 
and  probably  out  of  mind,  but  none  the  less  present  and  uncontrolla- 
ble; while  in  the  plating  bath  it  is  in  sight  and  controllable  more 
or  less,  at  the  will  of  the  attendant.  In  the  case  of  high  voltage  and 
large  ampere  currents  returning  to  their  source  of  generation,  it  is 
one  of  the  laws  of  electricity  that  where  a  current  has  two  paths  to 

*  "Electrolysis,"  Engineering  Record,  August  21,  1899. 

370 


ELECTROLYSIS  IN  FERRIC  BUILDINGS.  371 

• 

reach  this  point  (and  all  electrical  currents  have  two  paths),  the 
current  will  divide  and  return  to  its  source  in  the  direct  ratio  of  their 
conducting  capacity,  whatever  these  conductors  may  be.  Even 
with  large  and  well-bonded  metal  return  conductors  buried  in  the  earth 
or  in  conduits,  some  of  the  current  will  invariably  pass  by  way  of  the 
earth  and  reach  any  outlying  metallic  bodies.  The  low  voltage  of  .001 
to  .01  and  the  amount  of  amperes  will  determine  the  rate  of  corrosive 
effect  in  all  metal  in  their  course." 

The  advent  of  the  steel  building  almost  simultaneous  with  the 
introduction  of  the  dynamo,  has  added  not  another  form  of  corrosion, 
but  a  new  field  for  its  development  and  a  new  danger. 

The  principal  part  of  the  metal  in  steel  frame  structures  is  so 
embedded  in  masonry  as  to  render  inspection  of  its  condition  almost 
impossible.  The  pipe  systems  are  more  accessible,  but  are  never- 
theless at  all  times  a  ready  prey  for  electrolysis. 

Three  hundred  horse-power  of  electrical  energy  are  not  uncom- 
mon installations  for  light  and  power  in  one  building.  Whether  led 
in  from  the  outside,  or  generated  in  the  building  does  not  change 
the  effect,  which  is  to  disturb  the  normal  electrical  conditions  of  all 
metals  in  the  immediate  neighborhood  and  in  many  cases  those  far 
distant. 

In  the  return  of  this  energy  from  its  work  to  its  generating  source, 
if  the  pathway  is  not  made  perfectly  free  by  the  use  of  a  conductor  of 
adequate  size,  or  if  it  be  of  such  a  length  as  to  render  a  shorter  and 
better  circuit  through  other  objects  possible,  then  the  current  will 
jump  the  line  wholly  or  in  part.  On  the  new  route,  wherever  it  leaves 
the  metal,  another  jump  will  occur,  and  the  metal  will  be  corroded  at 
that  place,  and  not  where  the  energy  entered.  There  is  always 
moisture  enough  in  any  building  to  afford  adequate  oxygen  for  the 
corrosion. 

In  the  steel  frame  work  of  the  building,  the  electrolysis  will  be  at 
the  foot  of  the  columns  nearest  to  the  least  resisting  pathway  of  the 
current,  generally  at  a  point  impossible  to  locate  or  inspect,  and 
with  moisture  in  excess  to  make  a  good  cross-cut  and  dangerous 
circuit. 

In  the  iron  pipes  there  usually  will  be  a  jump  at  every  joint,  if  it  is 
made  by  the  hemp  gasket  and  lead,  or  by  a  hydraulic  cement  method. 
The  screwed  ends  of  wrought-iron  gas  and  water-pipes  also  are  affected 
by  the  difference  in  resistance  between  the  two  natures  of  the  same 
metal,  and  sheet  iron  used  for  shims  between  columns  and  girders 


372  ELECTROLYSIS  IN  FERRIC  BUILDINGS. 

have  been  found  to  be  the  cause  of  a  jump  corrosion,  particularly 
if  aided  by  the  presence  of  damp  dirt  or  other  substances. 

A  voltage  of  118  maintains  an  arc  of  one  inch  in  an  electric  arc 
light,  and  requires  1  H.P.  of  electric  energy,  and  fourteen  six- 
teen-candle-power  incandescent  lamps  represent  the  same  amount 
of  energy.  It  is  not  infrequent  to  find  an  arc  light  or  twenty  or 
more  incandescent  lights,  or  an  equivalent  energy  from  small  motors 
connected  to  the  pipe  systems  or  the  steel  frame  of  the  building. 
The  effect  of  these  strong  currents  is  to  set  up  a  corrosion  in  the  steel 
at  some  point  where  the  current  is  interrupted  on  its  return  to  the 
dynamo. 

Under  some  one  of  their  many  developments,  induced  currents 
are  strong  enough  to  corrode  metal,  even  if  the  main  current  or  return 
current  wires  are  adequate  for  their  duty.  Less  than  .005  volt  estab- 
lishes electrolysis,  the  amount  of  which  is  in  proportion  to  the  amperes 
present  and  not  to  the  voltage. 

Protection  from  the  effects  of  the  jump  of  the  current,  particularly 
in  the  lower  parts  of  a  steel  frame,  is  rendered  more  uncertain,  by 
reason  of  the  disturbing  action  of  electric  currents  from  adjoining 
sources  of  generation.  These  currents  finding  their  return  to  their 
source  of  generation  obstructed  from  any  cause,  form  a  short  or 
easier  circuit  that  often  lies  through  another  dynamo's  sphere  of 
action.  They  invade  its  field  and  disarrange  a  return  current  system 
that  at  first  might  have  been  adequate  for  its  duty,  but  is  not  able 
to  withstand  currents  from  its  neighbor  of  subsequent  installation. 

Twenty  or  more  of  these  electrical  installations  of  different  degrees 
of  voltage,  ampere,  and  work,  are  often  placed  within  a  compara- 
tively small  area.  Many  of  these  have  been  found  to  have  a  return 
wire  system  of  inadequate  size  or  of  faulty  insulation,  and  all  of  them 
subject  to  a  wide  range  of  fluctuation  in  energy  due  to  the  varying 
character  of  their  separate  work.  With  these  influences  at  work  at 
nearly  all  hours,  it  may  be  confidently  expected  that  the  near  future 
will  reveal  some  large  and  dangerous  examples  of  corrosion  in  steel- 
framed  buildings,  from  sources  that  thus  far  have  received  only  a 
cursory  consideration  and  no  prevention. 

Many  instances  are  on  record  showing  the  erratic  action  and  dan- 
gerous character  of  either  stray  or  direct  electrical  currents.  The 
United  States  Astronomical  Observatory  at  Washington,  D.  C., 
though  eligibly  situated  and  free  from  the  disturbing  influences  of  a 
large  city,  had  its  magnetic  observation  department  rendered  useless 


ELECTROLYSIS   IN  FERRIC  BUILDINGS.  373 

by  the  stray  electrical  currents  from  a  trolley  line  of  street  railway 
some  three-fourths  of  a  mile  distant.  This  branch  of  science  so 
closely  associated  with  the  daily  needs  and  welfare  of  mankind ; 
was  paralyzed  by  the  culpable  indifference  of  a  corporation  to  the 
requirements  of  science.  It  took  an  Act  of  Congress,  carrying  the 
imposition  of  a  heavy  fine  to  stop  the  nuisance.  The  Act  not  only 
prohibited  the  use  of  any  underground  water-  or  gas-pipes  as  means 
for  returning  the  trolley-line  currents  to  the  power  house,  but  also, 
forbade  the  connection  of  either  pole  of  a  railway  dynamo  in  any 
direct  manner  with  the  earth. 

Paints  furnish  neither  remedy  nor  protection  from  electrolysis. 
Paints  under  catchy  names  are  extensively  advertised  as  being  elec- 
trically inert,  or  insulating  in  charcter.  Such  names  and  state- 
ments are  misleading  and  unreliable.  No  paint  whose  pigment  is 
an  oxide  and  again  reducible  by  heat  to  a  metal,  is  non-electric  or 
passive  to  electrical  influences  in  any  degree  beyond  that  due  to 
the  difference  between  the  oxide  and  its  metal,  generally  about  50  per 
cent,  but  is  never  nil. 

Lampblack  and  graphitic  carbon  are  the  only  pigments  that  are 
partially  non-electric,  and  even  with  the  use  of  these  in  a  paint,  the 
coating  as  an  insulating  substance  is  governed  by  the  vehicle.  The 
vehicles  containing  the  resins,  fossil  gums  and  refined  bitumen  and 
combined  by  heat  into  a  varnish,  are  the  best  for  non-electric  paints. 
Tt  is  quite  unusual  to  find  them  in  use  on  account  of  their  cost,  while 
the  cheaper  grades  of  resins  and  resin-oils  used  in  the  vehicle  are 
only  insulating  up  to  a  certain  percentage,  when  they  become  con- 
ductors. 

All  of  the  vitreous  class  of  pigments,  such  as  slags,  hard-burnt 
brick,  tiles  and  slate,  are  conductors  in  their  pulverized  form,  and 
usually  act  in  a  paint  as  the  negative  electrode  to  concentrate  the 
electrical  energy  upon  the  covered  ferric  body.  The  thin  coating  of 
the  vehicle,  ToVo  to  TTTO"  mcn  m  thickness,  is  not  resistant  enough 
to  but  partially  insulate  the  pigment,  however  effective  the  vehicle 
may  be  in  mass  or  in  heavier  coatings  that  could  not  be  applied  cold 
with  a  brush. 

Electrolysis  inaugurated  beneath  such  coatings,  generally  throws 
them  off,  or  they  act  as  a  mask  to  conceal  its  ravages ;  while  inferior 
coatings  are  rendered  hard  or  porous  from  the  decay  of  the  vehicle  or 
pigment. 


374 


ELECTROLYSIS  OF   THE  PEORIA   STAND-PIPE. 


*  The  following  cuts  and  descriptions  illustrate  an  instance  of  the 
effect  of  corrosion  induced  by  stray  electrical  currents  that  caused 
the  destruction  of  a  water- works  stand-pipe  at  Peoria,  111.,  March  30, 
1900,  with  the  loss  of  life  of  two  persons  and  the  injury  of  fourteen 
others.  The  stand-pipe  was  60  feet  away  from  the  other  stand-pipes, 
and  more  than  a  mile  away  from  the  power  station.  Fig.  73  repre- 
sents a  sample  of  a  steel  sheet  from  the  stand-pipe,  showing  the  pit- 
ting in  the  sheet  around  the  edges  of  the  rivet-heads.  The  examina- 


Me'*. 


FIG.  73. — Pitting  of  steel  stand-pipe  sheet  around  the  rivets. 

tion  of  the  wreck  of  the  stand-pipe  showed  that  the  whole  inner  sur- 
face of  the  vertical  shell  appeared  to  be  thickly  covered  with  blisters 
resembling  in  outward  appearance  the  tubercules  sometimes  found 
inside  of  old  cast-iron  mains. 

A  similar  stand-pipe  on  the  East  Bluff  was  drained,  and  was  found 
to  be  similarly  pitted.  This  blistered  covering,  which  was  almost 
as  thin  as  paper,  was  composed  entirely  of  oxide  of  iron,  and  on 
brushing  it  away  the  black  paint  with  which  the  stand-pipe  had  been 
originally  coated  was  found  beneath  it.  The  paint  was  oftentimes 
almost  unbroken,  or,  at  least,  very  slightly  cracked.  When  the 


*  Excerpts  from  "Electrolysis  of  Underground  Metallic  Structures."  A  paper 
read  by  Mr.  Darney  H.  Maury,  Chief  Engineer  of  the  Peoria  (111.)  Water  Works, 
before  the  American  Water  Works  Association,  May,  1900.  Engineering  News, 
June,  1900;  also,  American  Gas  Light  Journal,  July  30,  1900. 


ELECTROLYSIS  OF   THE  PEORIA   STAND-PIPE.  375 

paint  was  brushed  off  the  pit  would .  be  disclosed,  considerably 
smaller  in  area  than  the  surface  covered  by  the  blister.  The  surface 
of  the  metal  in  the  pit  was  perfectly  bright  and  clean  and  its  fibre 
was  clearly  discernible.  Many  of  these  pits  were  more  than  |  inch 
in  depth.  They  were  slightly  more  numerous  in  the  West  Bluff  stand- 
pipe  than  in  the  East  Bluff  stand-pipe,  and  were  in  both  generally 
larger  and  deeper  on  the  lower  courses  of  the  vertical  shell. 

The  electrical  examination  relative  to  the  stand-pipes  was  conducted 
mainly  at  the  East  Bluff  stand-pipe,  which  was  still  in  service. 
A  flow  of  a  part  of  the  current  from  the  railway-line  was  clearly  traced 
through  the  earth  to  the  anchor-bolts  which  held  the  stand-pipe  to  its 
foundation,  as  shown  in  Fig.  74,  up  these  bolts  and  into  the  steel  of 
the  shell,  and  through  the  shell  and  from  its  inner  surface  to  the 
projecting  section  of  the  16-inch  flanged  cast-iron  pipe  which  served 
as  both  inlet  and  outlet,  and  which  connected  the  stand-pipe  to  the 
water-mains.  The  current  was  then  traced  along  this  pipe  and 
along  the  mains  to  the  power  station.  The  deflections  of  the 
volt-metre  needle  were  clearly  traced  to  the  railway  current,  being 
especially  influenced  by  the  cars  on  the  line  beyond  the  stand-pipe, 
and  when  the  cars  stopped  running  at  night,  the  movement  of  the 
needle  ceased.  Where  the  current  left  the  inner  surface  of  the  shell 
to  pass  through  the  water  to  the  inlet  pipe  it  made  the  pits  already 
described. 

Fig.  78  shows  the  interior  surfaces  of  three  sections  of  this  inlet 
pipe,  marked  A,  B,  and  C,  respectively,  the  positions  occupied  by 
these  sections  originally  being  shown  by  the  lettters  A,  B,  and  C  in 
Fig.  74.  An  examination  showed  that  strongly  marked  and  numer- 
ous pits  were  inside  the  sections  A  and  B,  while  the  inner  surface  of 
the  section  C  was  practically  as  smooth  and  perfect  as  though  new. 
When  the  condition  of  the  inside  of  these  three  sections  of  pipe  was 
first  noted,  it  was  hard  to  understand  why  A  and  B  should  be  pitted, 
while  C  was  unaffected.  A  closer  examination,  however,  showed 
that  in  the  flanged  joints  between  the  bottom  sheet  of  the  stand-pipe 
and  A  and  B,  respectively,  corrugated  copper  gaskets  were  used, 
while  the  pipe  B  was  separated  from  the  pipe  C  by  a  thick  rubber 
gasket;  and  that  under  the  nuts  and  heads  of  the  bolts  holding  the 
flanges  together,  there  were  grummets  or  wrappings  of  cotton  wick 
soaked  in  tallow. 

The  result  of  this  arrangement  was,  that  the  current  which  entered 
A  after  passing  through  the  water  from  the  inner  side  of  the  shell 


376 


ELECTROLYSIS  OF  THE  PEORIA   STAND-PIPE 


of  the  stand-pipe,  and  which  was  trying  to  return  along  the  inlet 
pipe  and  water-mains  to  the  power  station,  encountered,  at  the  joint 


FIG.  74. — Partial  section  of  Peoria  stand-pipe,  showing  course  of   electrical 

current. 

between  B  and  C,  the  rubber  gasket  and  the  grummets.     The  effect 
of  the  gasket  and  grummets  was  to  practically  invulate  the  section  C 


FIG.  75. — Interior  view  of  lengths  of  inlet  to  stand-pipe,  showing  pittings  in  A 
and  B,  and  effect  of  the  insulation  of  C. 


from  the  sections  A  and  B,  and  as  none  of  these  pipes  were  in  contact 
with  the  ground,  the  current  was  compelled  to  leave  the  pipes  A 


ELECTROLYSIS  OF   THE  PEORIA   STAND-PIPE. 


377 


and  B  and  travel  through  the  water  or  along  the  slimy  coating  of 
oxide  on  the  inside  of  the  pipes  around  the  joint  between  B  and  C, 
in  order  to  continue  on  its  journey.  As  the  current  was  not  leaving 
C,  this  pipe  was  not  injured,  but  the  current,  in  leaving  the  inner 
surfaces  of  A  and  B,  did  pit  them,  as  shown  in  the  photograph. 

The  experiments  conducted  since  the  destruction  of  this  stand-pipe 
have  determined  that  no  manner  of  packing  the  joints  in  an  under- 
ground cast-iron  water-  or  gas-pipe  line  affects,  only  in  a  small  degree, 
the  difference  in  potential  between  the  two  ends  of  the  connected 
pipes.  Whether  the  joints  were  well  or  poorly  calked,  the  pipes 
empty  and  dry,  or  full  of  water,  clear  or  muddy,  with  scale  on  the 
pipe  or  clean  surfaced,  the  drop  of  potential  around  the  joint  only 
varied  from  0.0145  to  0.008  volt,  and  the  general  average  resistance 
of  the  joints  was  about  96  per  cent  of  the  resistance  of  the  whole  line 
of  pipe,  and  the  resistance  of  the  joints  increased  with  age. 
Pitting  was  always  observed  where  the  shunt  of  the  electric  current 


(Current 


FIG.  76. — Electrolytical  pittings  on  12-inch  cast-iron  water-main. 

flowing  from  A  to  B.} 

left  the  metal  to  flow  around  the  joint,  and  this  corrosive  action  was 
as  marked  upon  the  inside  surfaces  of  the  pipes  as  upon  the  external 
surfaces;  but  from  the  conditions  could  not  be  observed. 
Wrought-iron  pipes  joined  by  the  usual  screw-thread  and  thimble 
connections  were  almost  as  universally  attacked  by  electrolytic 
action  at  the  joints  of  the  cast-iron  pipes.  The  difference  in  potential 
between  the  pipe  and  the  socket,  from  their  different  arrangement 
of  metallic  fibres,  resulted  in  the  faster  corroding  of  the  pipe  ends 
than  the  screwed  socket  or  thimble. 


378 


ELECTROLYSIS  OF  THE  PEORIA   STAND-PIPE. 


The  joints  in  the  cast-iron  pipes,  whether  coated  or  not  with  the 
usual  coal-tar  preparations  put  on  at  the  pipe-foundry,  had  little  or 
no  effect  to  insulate  or  protect  the  pipe  from  electrolytic  corrosion, 
which  generally  showed  in  the  form  of  blisters  or  like  the  usual  tuber- 


FIG.  77.— Electrolytical   pittings   no  inside   and   outside   of  4-inch  cast-iron 

water-pipe. 

cules  formed  on  water-pipes  by  the  action  of  water.  These  tuber- 
cules  when  broken,  and  the  material  under  them  analyzed,  showed 
22.3  to  23  per  cent  graphitic  carbon  and  47  to  47.7  per  cent  iron. 

The  soil  in  which  the  pipes  were  embedded  had  received  and 
was  impregnated  with  the  metal  (iron  or  lead)  corroded  by  the  electric 
current,  even  to  some  distance  from  the  pipe.  In  sections  of 
pipe  from  600  to  2000  feet  long,  there  were  several  zones  and  centres 
of  greater  action  than  on  the  pipe  in  general,  but  they  all  centred 
toward  the  nearest  generating  dynamo,  and  were  evidently  localized 
at  these  points,  from  the  greater  amount  of  electrical  energy  cast  off 
at  the  meeting  and  passing  points  and  switching  of  the  cars;  con- 
tiguous lines  of  cars  and  currents  from  other  sources  all  contributing 
in  the  most  erratic  manner  to  the  corrosive  result. 

Mr.   William  Work,  in  a   communication  to  the  Institution  of 


ELECTROLYSIS  IN  WATER  PIPES.  379 

Civil  Engineers,  1901,  reports  the  rapid  corroding  of  wrought-iron 
service-pipes  for  water  and  gas,  laid  in  a  light,  sandy  soil.  The 
water  service-pipes  corroded  in  seven  years,  so  as  to  need  renewal,  and 
the  gas  service  had  almost  completely  disappeared  at  the  end  of 
ten  years. 

Analysis  of  the  soil  disclosed  the  presence  of  common  salt,  mag- 
nesium chloride,  iron,  alumina,  silica,  lime,  and  posphates.  The  town 
where  the  pipes  were  laid  had  no  system  of  sewers,  and  during  the 
summer  season  the  streets  were  daily  watered,  and  as  the  streets  were 
level  the  water  was  quickly  absorbed.  The  subsoil  in  which  the  pipes 
were  laid  was  porous  and  alternated  from  dry  to  damp. 

Carbonic  acid  was  generated  from  the  chemical  action  of  the 
soil  and  attacked  the  pipes  as  stated.  The  trouble  was  confined  to 
the  wrought-iron  service-pipes;  the  cast-iron  pipe-mains  to  which 
the  service  pipes  were  connected  were  not  affected  in  any  noticeable 
degree.  Similar  pipe-services  laid  in  neighboring  towns  where  the 
soil  was  of  a  decomposed  granite  nature  were  comparatively  unin- 
jured after  a  period  of  twenty-  even  years. 

Salt  or  lime  in  any  soil  in  which  pipes  are  laid  necessarily  prove 
active  agents  to  promote  corrosion,  as  they  are  hygroscopic  in  nature ; 
and  if  alkaline  substances  are  also  present  in  the  form  of  ashes  and 
coal  cinders,  as  they  nearly  always  are  in  the  soil  of  towns,  the  life  of 
all  wrought-iron  work  buried  in  it  will  be  very  short,  even  with 
the  usual  crude  coal-tar  coatings.  Clay  puddle  around  such  pipes 
proves  a  good  protection,  as  pipes  so  protected  have  been  found 
practically  uncorroded  after  forty  years. 

Mr.  Chas.  W.  Rowe,  Secretary  of  the  Dayton,  Ohio,  Water  De- 
partment, reports  that  the  cast-iron  water-mains  laid  in  1891 
were  found  in  1900  so  greatly  affected  by  e  ectrolysis  as  to  endanger 
the  water-supply  of  the  whole  city.  Voltages  of  4.5  were  found  in 
many  parts  of  the  pipe  system. 

The  Annual  Report  of  the  Water  Department  shows  that  in  1899 
579  feet  of  6-inch  pipe  and  26  feet  of  4-inch  pipe  were  abandoned  on 
account  of  electrolysis. 

Mr.  Rowe  reports  that  in  1898  over  46,000  feet  of  the  water- 
pipes  from  4  to  16  inches  in  diameter  were  so  seriously  corroded  by 
electrolysis  from  the  trolley-line  currents,  that  in  some  cases  over 
one-half  of  their  strength  was  gone.  A  6-inch  pipe  became  useless  in 
five  years.  The  pipes  became  coated  with  a  graphite-like  sub- 
stance TV  or  more  inch  thick,  the  pebbles  and  stones  in  the  ground 


380 


ELECTROLYSIS  IN  WATER  PIPES. 


near  the  pipes  being  plated  with  the  same  substance.  About  |-{j  of 
the  electric  current  used  to  drive  the  trolley  cars  was  found  to  pass 
through  the  pipes  and  only  ^V  passed  by  the  street  rails  on  its  return 
to  the  dynamo. 

Fig.  78  shows  the  electrolysis  of  a  4-inch  cast-iron  water-pipe  at 
Reading,  Pa.  'V 


FIG.  78. 

No.  1.  Laid  22  years  or  about  18  years  before  the  advent  of  the 
trolley  lines  at  the  point  where  the  pipe  was  laid. 

No.  2.  Laid  thirteen  months. 

No.  3.  Laid  22  years.     Burst  when  uncovered  for  examination. 

Fig.  79  shows  a  16-inch  cast-iron  suction  pipe;  also  a  water  main 
from  Reading,  Pa.  The  pipes  are  samples  of  those  laid  300-800 
and  1000  feet  distant  from  the  street  trolley  lines,  and  all  were  over 
two  miles  distant  from  the  electric  power  station.  The  effect  of 
the  resistance  of  the  joint  packing  is  seen  in  the  corrosion  of  the 
ring  on  the  end  of  the  pipes;  also  in  the  general  corrosion  at  the 
ends  where  inclosed  in  the  bell. 

Fence  nails  were  driven  into  the  ends  as  easily  as  into  a  wooden 
post. 

Flakes  of  corroded  metal  3"Xl"  in  size  and  J-inch  in  thickness 
were  of  frequent  occurrence  in  the  Reading  pipes. 


ELECTROLYSIS  IN  WATER  PIPES. 


381 


" Electrolysis  of  Underground  Water-Pipes"  by  Mr.  F.  C. 
Kelsey,  Chief  Engineer,  of  Salt  Lake  City,  Utah,  is  a  condensed  report 
of  the  reports  from  the  chief  engineers  of  seven  cities  in  the  United 
States,  of  the  presence  of  electrolysis  in  their  water-supply  systems. 


FIG.  79. — 16-inch  cast-iron  suction  pipes  (page  380). 

Briefly  stated,  electrical  currents  of  low  potential,  .001  volt, 
were  found  and  were  enough  to  establish  electrolysis  that  under 
favorable  conditions  for  the  pipe  might  not  have  become  serious  in  a 
limited  period,  but  in  the  case  of  soils  carrying  salts  and  acids  of 
decomposing  materials  the  corrosion  from  electrolysis  was  materi- 
ally accelerated  and  increased  rapidly  as  the  voltage  rose  to  .01  volt. 
Currents  of  one-half  volt  destroyed  a  telephone  cable  in  a  few  months. 
A  minute  quantity  of  soluble  salt  in  the  soil  was  enough  to  start  the 
current  and  establish  the  electrolytic  point  or  points  in  the  metals, 
the  corrosion  of  which  continued  as  long  as  the  current  flowed.  In 
all  cases  where  the  water-pipes  or  the  metal- work  of  the  building  was 
positive  to  the  earth  or  any  surrounding  object,  the  electric  current 
flowed  in  that  direction  and  electrolysis  was  established  in  the  posi- 
tive element  of  the  couple,  wherever  it  was  situated.  It  was  noticed 
in  many  cases  that  the  lead  service  pipes  and  the  lead-packing  in 
the  water-mains  were  corroded  to  such  an  extent  that  excessive 


382 


ELECTROLYSIS  IN  WATER   PIPES. 


leakage  was  the  result,  and  the  pipe-joints  were  no  longer  able 
to  resist  the  pressure  of  the  water  wnen  it  was  over  20  pounds.  This 
corrosive  action  upon  lead  is  of  interest,  as  metallic  lead  has  been 
generally  considered  electro-passive,  and  is  used  for  the  outer  insulat- 
ing covering  for  the  cables  in  all  underground  conduits  for  electric 
lighting  and  power. 

The  Report  of  the  Board  of  Commissioners  of  Electrical  Subways, 
Brooklyn,  N.  Y.,  1894,  states  that  nearly  300  miles  of  lead-coated 
telephone  cables  were  rendered  useless  by  electrolysis  from  the  trolley 
currents  in  that  year.  Many  cases  of  corrosion  were  found  where 
the  lead  cable  was  incased  in  pitch  and  other  insulating  compounds. 

Mr.  A.  A.  Knudson,  E.E.,  reporting  the  electrolysis  of  a  48-inch 
diameter  water-main  in  the  city  of  Cambridge,  Mass.,  found  vol- 
tages of  25,  and  amperages  of  30-50-80  and  90  at  many  points  of  the 
water-supply  system. 

Fig.  80,  Electrolysis  of  a  6-inch  cast-iron  water-pipe  at  Provi- 
dence, R.  I.  The  pipe  was  i-inch  thick  when  laid  and  had  been  in 
service  seven  years. 


FIG.  80. — Electrolysis  of  a  6-inch  cast-iron  pipe  at  Providence,  R.  I. 

Fig.  81  shows  the  electrolysis  in  one  end  of  a  steel  truss  for  a 
trolley  railway  bridge  at  Providence,  R.  I.  Both  ends  of  both  trusses 
were  similarly  corroded  near  the  ground  line. 

The  special  committee  of  the  American  Water  Works  Associa- 
tion, to  whom  the  subject  of  "Electrolysis  of  Underground  Water- 
pipes"  was  referred,  reported  at  the  Richmond,  Va.,  meeting  of 
1900,  the  result  of  their  investigations:  "That  with  the  best  bonded 


ELECTROLYSIS  IN   WATER   PIPES. 


383 


connection  of  the  rails,  including  even  the  welded  joint,  it  was 
impossible  to  secure  the  return  of  all  of  the  current  from  a  single 
trolley  railway-line  to  its  source  of  generation.  Some  of  the  current, 
under  the  law  of  divided  currents,  would  invariably  leave  the  rails 
and  seek  another  source  of  return  through  near-by  metal.  The 
smallest  measure  of  difference  in  potential  between  two  metallic 
bodies  was  sufficient  to  produce  and  maintain  electrolysis  in  one 
of  them." 


FIG.  81. — Electrolysis  of  a  steel  bridge  truss. 

Dr.  Leybold's  paper,  " Electrolysis  of  Gas-pipes,"*  states:  "The 
pipes  when  laid  were  protected  with  canvas  soaked  in  boiled  coal- 
gas  tar,  and  the  destruction  of  the  pipes  was  more  rapid  than  where 
they  were  laid  without  the  canvas  coating.  New  pipes  laid  with 
canvas  and  tar  coatings  to  replace  the  old  ones  were  perforated  into 
holes  in  seven  to  eight  months." 

The  annual  report  of  Mr.  Wm.  Jackson,  City  Engineer  of  Boston, 
Mass.,  states  that  ToVo  °f  a  vo^  was  sufficient  to  cause  electrolysis, 
and  some  of  the  most  serious  cases  of  electrolytic  action  in  the  city 
water-mains  were  where  only  1.5- volt  pressure  existed  between  the 
ground  and  the  pipes. 

*  American  Gas  Light  Journal,  September  30,  1901,  p.  526. 


384  ELECTROLYSIS  OF  GAS  PIPES. 

Mr.  L.  Holman,  Water  Commissioner  for  the  city  of  St.  Louis; 
Mo.,  calls  attention  to  the  corrosion  of  48-inch  diameter  water-mains 
in  that  city,  that  have  been  eaten  away  in  many  places  for  one-half 
inch,  and  could  be  cut  as  easily  as  plumbago.  The  danger  arising 
from  the  bursting  of  such  a  pipe  is  apparent. 

The  practical  effect  in  the  corrosion  of  underground  gas-mains 
and  wrought-iron  service-pipes,  principally  those  of  small  diameter, 
is  noted  in  the  Official  Reports  of  the  Gas  Bureau  of  the  city  of 
Philadelphia,  where  the  loss  from  leakage  in  the  form  of  unaccounted- 


L  FIG.  82. — Exterior  of  a  pipe  injured  by  electrolysis,  Springfield,  111. 

for  gas,  for  a  period  of  ten  years,  was  $5,750,000,  and  for  the  years 
1891  to  1895  averaged  two  millions  of  cubic  feet  per  day. 

The  Brooklyn  Union  Gas  Company  (Brooklyn,  N.  Y.)  has  about 
760  miles  of  gas-mains  of  all  sizes,  and  280  miles  of  wrought-iron  gas 
service-pipes.  The  latter  and  their  fittings  are  found  to  be  badly 
corroded  wherever  uncovered  for  examination.  Electrolysis  from 
stray  electrical  currents  is  manifest  in  many  cases.  Thirty-eight 
service-pipes  in  one  street  block  were  completely  destroyed  in  three 
years.  The  cast-iron  mains  are  reported  to  be  generally  in  a  good 
condition  so  far  as  electrolytic  action  is  concerned,  except  in  a  few 
cases  in  what  is  called  "the  dangerous  district;"  that  is,  in  the 
vicinity  of  the  electric-station  power-houses. 

The  loss  of  gas  from  all  of  the  underground  systems  in  this  city 
in  1899  amounted  to  13  per  cent  of  the  total  yearly  output  (4,500,- 
000,000  cubic  feet),  or  a  loss  of  585,000,000  cubic  feet. 

Other  cities  in  the  United  States  show  similar  conditions  in  their 
gas  systems.  The  ordinary  corrosion  of  underground  metal  has 
been  materially  increased  since  the  advent  of  electric  street  railways, 
however  thoroughly  the  rails  are  bonded  and  used  for  the  return 
current. 


ELECTROLYSIS  OF   WATER  AND  GAS  PIPES. 


385 


Lengths  of  pipe-mains  over  three  miles  long  are  reported  to  have 

corroded  to  such  an  extent  that  the  whole  pipe-line  had  deteriorated 

50  per  cent  in  four  years.     The  voltage  in  this  line  was  from  2  to  9 

positive.     At  a  voltage  averaging  4.5,  a  6-inch  pipe  became  useless 

in  five  years. 


10 


FIG.  83. — Lead  water  service -pipes  and  telephone -cable  coverings  in 
Brooklyn,  N.  Y. 

Water-mains  that  were  laid  and  tested  to  withstand  a  pressure  of 
over  300  pounds  to  the  square  inch,  at  the  end  of  four  years  leaked  at 
almost  every  joint  at  150  pounds'  pressure.  The  voltage  was  4.5, 
and  the  lead- joints  were  badly  corroded. 

Electrolysis  of  water-pipes  at  Kansas  City,  Mo.,*  Mr.  G.  B.  Wing, 
Superintendent  of  the  Metropolitan  Water  Works,  reports  that  speci- 
mens of  the  soil  at  a  distance  of  two  inches  from  some  of  the  corroded 
pipe  showed  4.67  per  cent  of  iron,  and  at  a  distance  of  one  foot,  2.65 
per  cent. 

The  corrosion  of  wrought-iron  and  lead  pipes  was  more  rapid  than 
that  of  cast-iron  pipes ;  the  amount  of  corrosion  in  all  cases  depended 
upon  the  amperage  of  the  current. 

The  electrical  resistance  of  the  ordinary  lead  and  oakum-packed 
joints  in  the  pipes  was  found  to  range  from  110  to  200  times  that 
of  the  pipe  itself. 

Variations  in  the  resistance  at  the  joints  ranged  from  0.0264  to 


*  Engineering  Record,  Vol.  XL,  No.  11,  August,  1899,  p.  239. 


386    ELECTROLYSIS  OF  WATER  PIPES  AND  STREET  RAILS 

0.0322  oh.n,  and  in  a  section  of  25  lengths  of  4-inch  pipe,  averaged 
0.11  ohm. 


FIG.  84.— Effect  of  electrolysis  on  6-inch  cast-iron  pipes,  Kansas  City,  Mo. 

" Wandering  Electricity  in  New  York  City."*  A  report  by 
Mr.  A.  A.  Knudson,  E.E.,  of  an  electrical  survey  of  the  section  of 
New  York  City  at  Third  Avenue  and  135th  Street,  where  a  trolley- 
line  had  a  terminus  in  front  of  an  elevated-railway  station.  There 
was  a  difference  of  2  volts,  rising  to  10  volts  at  times,  between  the 
trolley  tracks  and  the  nearest  railway  column,  and  a  difference  be- 
tween the  trolley  tracks  and  the  nearest  gas-main  of  5  volts. 

In  removing  the  rails  of  the  trolley-line  the  effects  of  the  passage 
of  the  current  from  them  to  the  gas-main  and  elevated-railway  struc- 
ture were  shown  by  the  corrosion  of  the  70-pound  rails.  The  base 
of  the  rails,  originally  4  inches  wide,  was  corroded  away  to  2f  inches 
wide  near  the  ends,  the  edges  of  the  flanges  being  corroded  to  knife 
edges  for  several  feet  back  from  the  ends. 

Fig.  85  shows  a  section  of  the  rails  at  one  end. 


FIG.  85. — Electrolysis  of  a  street-railway  steel  tee-rail. 

The  wrought-iron  gauge- ties  originally  li"Xf"  in  section  were 
corroded  completely  away  in  the  centre,  and  but  one  was  found  near 
the  station  that  was  unaffected  from  end  to  end. 

*  Engineering  Record,  Vol.  XXXVIII.  No.  23,  November  5,  1898,  p.  500. 


ELECTROLYSIS  OF  STREET  RAILS.  387 

In  the  current  at  the  terminal  that  passed  to  the  water-mains 
and  to  the  elevated-railway  structure,  there  was  a  difference  of  from 
2  to  2.5  volts.  At  one-fourth  of  a  mile  away  the  current  all  passed 
to  the  elevated-railway  structure,  ran  a  fourth  of  a  mile,  then 
returned  to  the  water-pipes  and  changed  again  to  the  railway  struc- 
ture in  about  half  a  mile. 

The  same  conditions  were  found  to  prevail  on  an  opposite  section 
of  the  elevated-railway  structure,  extending  for  about  a  mile  in  the 
opposite  direction  from  the  trolley  terminal. 

The  difference  in  potential  between  the  elevated-railway  columns 
and  the  street-trolley  rails  and  water-mains  ranged  from  1.30  to  1.50 
of  a  volt,  and  indicated  that  the  current  came  from  an  electric  light- 
ing station.  It  was  also  shown  by  the  tests  that  a  trolley-line  using 
the  rails,  water  and  gas-mains  for  its  return  service,  can  spread  the 
corrosive  influences  for  a  mile  in  either  direction  through  the  various 
subway  conduits,  pipes,  and  elevated-railway  structures;  also  that 
the  conductivity  of  a  50-pound  street  or  tee-rail  is  about  equal  to 
a  copper  rod  1  inch  in  diameter,  or  five  No.  000  B.  and  S.  copper  wires. 

Tests  applied  to  the  Brooklyn  Bridge  suspension  cables  showed 
that  generally  there  were  3  volts  positive  to  the  rails  of  the  trolley 
railway  on  the  structure.  The  effect  of  these  currents  upon  the 
anchorages  of  the  bridge  led  to  a  number  of  tests  of  the  upper  ends  of 
the  anchorage  metal.  The  tests  are  believed  by  the  bridge  engineers 
to  show  "that  no  damage  such  as  might  be  expected  from  corrosion 
of  underground  metal  has  thus  far  taken  place." 

A  wise  distinction  between  corrosion  and  electrolytic  action. 
Had  the  question  of  the  corrosion  of  the  rails  in  the  street  tracks  been 
put  to  the  trolley-railway  engineer  corps,  they  would  probably  have 
been  positive  that  no  such  corrosion  was  present  or  possible;  in  fact, 
they  were  indifferent  to  or  ignorant  of  the  corrosion  until  the  exam- 
ination by  Mr.  Knudson. 

It  required  the  public  evidence  of  a  half-dozen  of  broken  suspen- 
sion rods  and  panels  of  sunken  railway  tracks  to  convince  the  Brook- 
lyn Bridge  engineers  that  a  serious  case  of  neglect  and  corrosion 
existed  in  the  structure,  and  had  progressed  far  enough  to  be  dan- 
gerous to  it,  ere  a  few  long-neglected  repairs  were  made. 

That  that  neglect  does  not  include  the  anchorage  metal  is  by  no 
means  certain.  There  is  absolutely  no  plan  in  the  many  suspension 
bridges  erected  that  affords  any  practical  means  to  ascertain  the 


388        ELECTROLYSIS  OF  SUSPENSION-BRIDGE  CABLES. 

state  of  the  lower  members  of  the  anchorage  system,  or  of  arresting 
corrosion  or  electrolysis  in  them  if  found. 

Iron  and  steel  bodies  exposed  to  conditions  similar  to  bridge 
anchorage  metal  have  been  found  badly  corroded  within  a  few  years 
after  being  placed  in  position,  and  there  is  no  reason  to  infer  that 
any  bridge  anchorage  will  be  an  exception. 

The  rate  of  corrosion  from  natural  causes  has  been  fairly  deter- 
mined. In  anchorage  work  this  will  be  increased  by  any  electrical 
currents  that  may  reach  them,  and  it  is  inevitable  that  they  do  reach 
them,  and  no  means  of  preventing  it  now  exists. 

The  decay  of  metal  by  electrolysis  has  been  approximately  ascer- 
tained. The  escape  of  the  voltages  and  amperes  used  in  street-rail- 
way service  is  twenty  times  that  necessary  to  induce  ferric  corrosion 
and  often  more  than  twice  as  much  as  is  necessary  to  decompose 
water  in  mass. 

A  current  of  0.3  ampere  is  sufficient  to  corrode  a  lead  covering 
to  a  cable  or  the  lead  in  a  pipe- joint.  Electrical  engineers  report 
cases  where  the  lead  covering  of  cables  has  been  destroyed  in  six 
weeks  after  laying. 

A  potential  of  TTFV^  of  a  volt  is  all  that  is  required  to  induce  ferric 
corrosion  two  miles  from  the  dynamo. 

A  difference  in  voltage  of  20  volts  has  been  found  between 
the  two -ends  of  the  Brooklyn  Bridge  cables,  and  the  difference  in 
voltage  ranges  from  0.75  to  3  volts  at  all  hours  and  at  all  times  in  the 
day  whenever  tested,  and  is  always  found  electro-positive  to  the 
ground. 

So  long  as  electricity  obeys  the  known  laws  pertaining  to  its  genera- 
tion and  transmission,  it  will  select  the  line  of  least  resistance,  though 
it  may  not  be  the  shortest  in  returning  a  major  part  of  the  current 
to  its  individual  source  of  generation.  It  will  also  divide  en  route, 
pick  up  other  electric  currents  in  the  most  erratic  manner,  and  deposit 
them  in  unexpected  places,  generally  inaccessible  for  observation 
or  repairs. 

The  large  amounts  of  voltage  and  amperes  used  in  railway-motor 
systems  render  stray  electric  currents  more  certain  and  electrolysis 
more  constant,  even  if  a  "shunt"  of  the  current  from  any  adjoining 
bridge  cable  or  structure  were  possible.  At  the  present  state  of  the 
electrical  art  this  "cut-off"  is  practically  not  feasible. 

The  river  that  separates  the  two  anchorages  compels  the  bridge 
cables  to  act  as  conductors  for  the  electric  currents  present  at  all 


ELECTROLYSIS  OF  SUSPENSION-BRIDGE  ANCHORAGES.   389 

times  in  the  earth  and  air  and  never,  or  but  momentarily,  of  the  same 
potential. 

Hundreds  of  electric  installations  of  a  great  diversity  of  power 
surround  these  bridges  and  provide  a  cause  of  danger  that  at  present, 
if  known  or  suspected,  has  no  remedy  or  safeguard. 

The  future  results  of  electrolysis  on  all  suspension  bridges  may 
as  well  be  recognized  now,  rather  than  be  left  till  the  inevitable  catas- 
trophe befalls. 

The  corrosion  of  ferric  bodies,  not  aided  by  electrolysis,  is  known 
to  be  progressive,  being  nearly  50  per  cent  more  the  second  year 
than  the  first,  and  so  on  for  each  succeeding  year. 

During  the  construction  of  the  Britannia  Bridge  over  the  Menia 
Straits,  some  rejected  plates  T7g  and  f  inch  thick,  were  left  unpro- 
tected and  exposed  to  the  spray  and  wash  of  the  sea.  In  two  years 
they  had  corroded  so  that  they  could  be  swept  away  with  a  broom. 

A  few  pieces  of  ironwork  embedded  in  mortar  or  walled  in  some 
ancient  building,  or  an  old  water-gate  here  and  there,  in  some  very 
favorable  situation,  may  have  remained  uncorroded,  but  there  is 
little  unquestionable  proof  that  iron  or  steel  in  the  form  adopted 
for  bridges  or  structural  frame-work  will  last  more  than  two  hun- 
dred years. 

In  the  Niagara  Falls  and  the  Alleghany  River  suspension  bridges, 
after  about  twenty-five  years  of  duty,  an  inspection  showed  that 
some  of  the  wires  in  the  outer  strands  of  the  cables  outside  of  the 
anchorages  were  corroded  through,  but  the  second  and  interior  wires 
were  sound.  The  reason  assigned  for  the  corrosion  of  the  outer  strand 
wires  was  that  the  " creep"  of  the  individual  wires  under  the  varying 
strains  due  to  the  load  and  constant  changes  in  temperature  had 
worn  away  the  boiled  linseed-oil  and  other  coatings  applied  when 
the  wires  were  strung  and  allowed  atmospheric  moisture  to  reach 
them. 

It  is  now  proposed  to  abandon  the  boiled  oil  or  paint  coatings  of 
the  cables  and  to  use  a  mixture  of  vaseline  and  plumbago.  When 
the  wires  are  strung  and  ready  to  bunch  into  strands  and  cables,  all 
of  the  interstices  are  to  be  filled  as  far  as  possible  with  this  stiff  un- 
drying  mixture,  that  is  to  act  as  a  lubricant  for  the  inevitable  creep 
of  the  wires,  also  as  a  protection  from  corrosion. 

In  all  wire-wrapped  cables  there  is  an  appreciable  space  between 
the  wrapping  and  the  cables,  caused  by  the  drying  and  shrinkage 
of  the  boiled  oil  coatings  applied  during  their  construction.  The 


390  CORROSION  IN  SUSPENSION   BRIDGES. 

daily  changes  in  temperature  of  the  cable  wrappings  are  greater  than 
the  mass  of  wires  they  cover,  hence  with  the  changes  due  to  the 
extremes  of  summer  heat  and  winter  cold,  they  necessarily  prove  an 
element  of  weakness  in  providing  a  foundation  for  the  paint  coat- 
ings that  are  supposed  to  seal  the  cables  water-tight. 

Mr.  Robert  Mallet,  C.E.  (Dublin),  made  a  report  to  the  British 
Association  in  1858  on  paints  for  bridge  and  cable  iron  work:  "That 
he  had  tested  ten  of  the  best  and  most  reliable  ferric  paints  and  var- 
nishes then  known,  and  not  one  of  them  remained  adherent  and 
undecomposed  for  a  single  year  under  water.  In  moist  air,  and 
under  conditions  resembling  English  sea-coast  fog,  their  state  was 
not  much  better.  The  presence  of  moisture  even  to  the  extent  of 
a  partial  saturation  of  the  air,  developed  a  fungus,  the  decomposition 
of  which  was  almost  as  fatal  to  the  life  of  a  paint  as  immersion  in 
sea- water." 

Government  authorities  state  that  there  are  over  300  suspen- 
sion bridges  in  Europe,  of  a  great  variety  of  spans  and  industrial 
importance;  many  of  them  having  eyebars  instead  of  wire  cable 
suspensions.  It  is  also  stated  that  the  life  of  the  wire  cables  and 
anchorages  have  been  found  to  be  precarious,  for  oxidation  was 
in  progress  in  the  interior  of  the  cables,  while  the  anchorages  were 
weakened  from  the  attack  of  some  element  "not  at  present  defined  " 
(evidently  electrolysis) .  That  there  was  no  reliance  to  be  placed  on 
the  preservation  methods,  or  any  certainty  that  they  had  effect  on 
the  life  of  the  structure  beyond  twenty-five  years. 

The  failure  of  the  Angiers  wire  cable  suspension  bridge  showed 
that  it  was  impossible  to  keep  the  hydrate-of-lime  coating  used  there 
in  immediate  contact  with  the  anchorage  metal.  Moisture  and 
earth  acids,  carbonic  acid  from  the  atmosphere  reached  the  metal, 
and  the  lime-coating  was  practically  useless  to  prevent  corrosion. 

M.  Bernadeau  in  the  "Annales  des  Fonts  et  Chausseur/'  1881, 
refers  to  a  bridge  in  which  of  the  150  wires  forming  a  cable  only  15 
were  in  good  condition,  the  rest  were  brittle  as  glass.  The  bridge 
had  been  in  use  less  than  forty  years. 

Two  other  suspension  bridges  of  short  span  fell  after  twenty-six 
and  twenty-eight  years'  duty. 

The  suspension  bridge  over  the  Ostrawitza  River  at  Mahrisch- 
Ostra,  finished  in  1851,  failed'  in  1886  from  a  fracture  of  one  of  the 
anchor  chains.  The  metal  in  the  chain  had  thoroughly  changed  its 
character  by  corrosion,  so  that  it  could  be  crushed  by  the  hand. 


CORROSION  IN  SUSPENSION  BRIDGES.  391 

The  anchor-bars  in  this  bridge  consisted  of  12  links,  one  of  which 
was  completely  corroded  away  and  the  others  were  reduced  to  about 
one-sixth  of  the  original  size.  The  original  sectional  area  of  the  anchors 
was  24.4  square  inches,  but  had  corroded  to  about  4  inches.  An 
official  examination  and  report  of  the  strength  and  condition  of  the 
bridge  was  made  in  1885,  one  year  before  its  failure,  which  stated 
that  "The  bridge  has  been  examined  in  all  its  parts  and  is  in  good 
and  safe  condition."  A  squadron  of  Uhlans  went  down  with  the 
bridge. 

An  examination  of  the  wire  cables  of  a  suspension  bridge,  where 
coal-tar  and  lime  had  been  used  to  coat  the  wires,  also  to  fill  the 
interstices  between  them  where  the  cables  entered  the  anchorages, 
showed  that  these  cables  were  wrapped  with  TVmch  diameter  wire 
and  then  a  canvas  jacket  saturated  with  coal-tar  and  lime  placed  over 
them.  After  less  than  twenty  years'  duty  the  tar  had  partially 
decomposed  and  disappeared  and  the  cavities  were  filled  with  a 
dirty,  grayish  liquid.  The  wrapping  wire,  also  the  seizing  wire  on 
the  strands,  were  in  many  cases  rusted  through,  and  the  cable  wires 
deeply  pitted.  The  damage  to  all  the  wires  extended  about  three 
feet  upward  and  outward  from  the  cable  anchorages.  Beyond  this 
there  was  a  little  rust,  but  no  pitting,  and  still  further  from  the  anchor- 
age the  paint  on  the  interior  of  the  cable  was  gummy  and  undried. 

*  French  engineers  of  reputation  now  prohibit  the  use  of  white- 
lead  or  any  quick-drying  paints  on  anchorage  cables.  The  failure  of  a 
number  of  suspension-bridge  cables  in  France  was  directly  traceable  to 
the  use  of  that  kind  of  paint.  Chalking  and  cracking  of  the  coating, 
owing  to  the  ceaseless  changes  of  temperature  to  which  they  and  the 
cables  were  exposed,  admitted  water  and  held  it,  and  corrosion  of  the 
wires  at  or  near  their  lowest  position  in  the  cables  was  the  result. 

Euphorbium  paints  possessing  elasticity,  tenacity,  and  a  quality 
that  prevents  them  from  drying  bone-hard  and  becoming  brittle, 
have  proven  the  best  paints  used  by  French  engineers  for  cable  or 
other  ferric  work.  Euphorbium  being  of  a  non-corrosive  and  anti- 
fouling  nature,  prevents  the  growth  of  atmospheric  fungus,  the 
decomposition  of  which  produces  an  acid  highly  corrosive  to  iron. 

Other  resinous  or  varnish  paints  dried  hard  and  brittle  and  soon 
cracked.  Mastic  proved  to  be  the  best  of  all  the  so-called  copal 
gums  for  a  bridge-cable  varnish  paint. 

*Le  Genie  Civil,  1881. 


392  CORROSION  IN  SUSPENSION  BRIDGES. 

The  failure  of  so  many  wire  cable  suspension  bridges  that  have 
been  in  duty  less  than  fifty  years  whose  collapse  can  be  attributed 
to  corrosion  or  electrolysis  and  not  to  overloading,  shows  the  impera- 
tive necessity  of  having  the  cable  and  particularly  the  anchorage 
metal  accessible  for  inspection  at  any  time.  Corrosion  of  cables  and 
metals  in  the  air  may  be  in  part  observed,  but  electrolysis  occurring 
in  the  lower  and  hidden  parts  of  the  anchorage,  and  not  reparable 
nor  preventable,  should  be  guarded  against  by  a  metallic  connection 
at  the  anchor-plate  end,  that  will  lead  off  all  electric  currents  and 
extinguish  them  in  the  earth  and  not  in  the  metal  of  the  structure. 
This  connection  can  be  renewed  when  corroded,  and  all  shunts  or 
attempted  cut-offs  of  the  current  above  the  ground  line  avoided. 
In  the  case  of  divided  currents,  cut-offs  have  been  found  to  be  un- 
reliable. 

Cement  coatings  or  concrete  cannot  retard  electrolysis  if  any 
moisture  is  present.  Mr.  Eiffel  found  the  iron  rag-bolts  placed  in 
fortification  masonry  two  hundred  years  ago,  had  enlarged  from 
two  to  two  and  a  half  times  their  original  diameter  by  rusting  in 
the  mortar  in  a  dry  location. 

Rust  once  established,  carries  within  itself  the  elements  for  a 
ceaseless  life.  Even  in  a  glass  bottle  rust  begets  rust.  Hydrated 
rust  carries  over  20  per  cent  of  moisture,  and  so  long  as  it  can  attack 
a  fresh  surface  of  iron  and  cast  off  the  thin  film  of  oxide  as  it  forms, 
it  will  release  enough  oxygen  to  begin  another  cycle  of  action. 

Farraday's  law  of  the  corrosion  of  metal  in  weak  acidulated 
solutions  and  electrical  energy  applied  to  the  anode  is  1.0448  grains 
of  iron  per  square  foot,  per  ampere  hour.  The  life  of  any  ferric  body 
can  thus  be  approximately  ascertained  before  its  construction.  The 
methods  and  means  for  its  preservation  should  receive  the  most  care- 
ful consideration  of  the  engineer  and  others  responsible  for  its  pro- 
tection. That  its  preservation  is  more  difficult  than  its  planning 
or  construction  does  not  remove  this  serious  responsibility. 

The  borough  of  Brooklyn  (New  York  City)  has  about  800  miles 
of  water-mains  of  all  diameters  from  4  to  48  inches.  Many  of  these 
pipes  in  the  early  construction  of  the  water-works  were  cast  in  Glas- 
gow from  a  firm  close-grained  cast  iron  which  showed  a  white  sur- 
face on  fracture,  indicating  a  large  amount  of  combined  carbon  in 
the  metal.  Many  miles  of  these  pipes  were  also  coated  with  Dr. 
Angus  Smith's  anti-corrosive  compound,  as  before  mentioned  in 
this  work.  Previous  to  the  year  1900  but  few  cases  of  electrolysis 


ELECTROLYSIS  OF  UNDERGROUND  METAL.  393 

were  reported  in  the  water-mains  of  this  city.  The  apparent  freedom 
from  electrolysis  was  attributed  to  the  sandy  soil  in  which  the  pipes 
were  laid,  also  to  the  composition  of  the  cast  iron. 

Scotch  gray  or  forge  iron  was  thought  to  be  exempt  from  corro- 
sion, and  the  Roebling  bridge  anchor-plates  were  made  from  this 
brand  of  cast  iron  and  placed  in  the  anchorages  under  this  idea. 
But  many  of  the  pipes  were  cast  in  American  foundries  from  American 
cast  iron,  and  but  little  difference  in  their  corrosion  and  that  of  the 
Glasgow-made  pipes  had  ever  been  noticed.  After  the  effect  of  cor- 
rosion by  electrolysis  had  been  noticed,  to  determine  whether  the 
composition  of  the  cast  iron  had  any  power  to  prevent  it,  pieces  were 
cut  from  the  foreign  and  American  cast-iron  pipes,  also  from  soft 
cast  iron  containing  but  little  combined  carbon  and  more  graphite 
than  the  Scotch  irons,  and  used  as  anodes  in  various  electrolytic  cells. 
The  electrolytes  consisted  of  samples  of  earth  from  various  parts  of 
the  city,  moistened  with  distilled,  hydrant,  and  sea-water.  The  cells 
were  exposed  to  the  action  of  currents  of  different  voltage  and 
amperage. 

In  every  case  the  anode  was  corroded,  showing  conclusively  that 
there  is  no  immunity  from  electrolysis  of  cast  iron  used  for  water-pipes, 
because  of  its  chemical  composition. 

It  was  determined  by  the  observation  of  the  water-works'  engi- 
neers that  the  tubercular  corrosion  on  the  water-pipes  when  unpro- 
tected other  than  by  the  usual  thin  coal-tar  or  bitumen  pipe  dips 
was  at  the  rate  of  about  TTTUT  °f  an  mcn  vearly>  there  being  a  differ- 
ence in  the  rate  of  corrosion  in  the  pipes  of  different  metals,  markedly 
in  favor  of  the  close-grained,  white  firm  irons. 

Summarizing  the  report  of  many  other  water-works'  engineers, 
it  appears  that  corrosion  from  electrolysis,  tubercules,  or  from  other 
causes  is  more  rapid  in  wrought-iron  than  in  cast-iron  pipes,  irre- 
spective of  the  kind  of  soils  they  are  buried  in  or  to  whatever  influences 
they  may  be  exposed. 

The  small  amount  of  electrolysis  in  the  city  of  Brooklyn  gas- 
and  water-mains  was  finally  attributed  by  Prof.  Samuel  Sheldon* 
to  the  presence  of  the  hard,  thin,  vitreous  scale  formed  on  them  at 
the  moment  of  casting  in  green  sand  molds,  and  that  this  scale  was 
a  non-conductor  of  electricity.  This  scale  is  similar  to  that  noted  on 

*  Brooklyn  Pol.  Inst.  Trans.  American  Institute  of  Electrical  Engineers, 
May,  1900. 


394  ELECTROLYSIS  OF   UNDERGROUND  METAL. 

car- wheels  and  in  connection  with  mining-pipes;  it  has  been  found 
to  retard  corrosion  due  to  sulphureted  water,  and  has  been  referred 
to  on  page  328. 

A  piece  of  the  sand-coated  pipe  was  covered  with  an  insulating 
paint,  but  leaving  exposed  a  small  area  of  the  silicate  coating.  This 
pipe  was  made  the  anode  in  an  electrolytic  solution.  Less  current 
flowed  through  the  solution  under  a  given  E.M.F.  than  under  similar 
conditions  with  an  anode  from  the  same  piece  of  pipe,  but  exposing 
a  clean  iron  surface  of  the  same  area  to  the  same  currents.  In 
some  of  the  experiments,  no  current  at  all  passed  the  scale  until 
the  voltage  was  raised  to  a  number  of  ohms.  The  water-pipes  coated 
with  Dr.  Angus  Smith's  compound  appeared  to  be  less  affected  by 
electrolysis  than  the  pipes  not  coated.  The  insulating  quality  of 
the  compound  added  to  the  power  of  the  silicate  coating  to  resist  the 
stray  electrical  currents  of  low  potential.  In  certain  districts  of 
the  city  where  high  potential  currents  reached  the  pipes,  electrolysis 
was  present,  but  concealed  by  the  firm  and  unbroken  coating  of 
Dr.  Smith's  and  other  heavy  anti-corrosive  coatings  and  was  the 
more  dangerous  on  this  account. 

In  every  city  in  which  electric  street  railway,  lighting,  and  power 
service  is  developed,  there  will  be  a  number  of  districts  corresponding 
to  the  number  of  power  stations  and  plants  for  individual  electrical 
generation.  Each  one  of  these  installations  will  draw  currents  from 
its  own  district  that  can  generally  be  very  closely  defined  in  the 
ordinary  working  of  the  station.  But  these  boundaries  become  very 
irregular,  daily  and  hourly,  from  the  varying  nature  of  the  currents 
required  for  the  work  to  be  done  in  them  respectively.  A  difference 
of  potential  has  been  noted — as  high  as  40  volts  between  different 
points  in  the  same  district  or  between  adjoining  districts.  Hence 
these  boundaries  are  always  shifting  to  a  greater  or  less  extent  at  all 
times.  It  matters  but  little  from  which  district  the  current  reaches 
underground  metal  or  what  its  potential,  electrolysis  is  assured  in 
every  case. 

Where  electrical  installations  of  a  known  amperage  of  40,000 
to  50,000  are  in  daily  use,  there  will  inevitably  be  some  leakage  of 
the  direct  and  return  currents  as  well  as  a  certain  energy  in  the  induc- 
tion currents,  always  present  for  the  corrosion  of  metal,  whether 
under  ground  or  partly  under  ground  and  partly  in  the  air.  Perfect 
insulation  from  one  or  more  or  all  of  these  currents  is  absolutely 
impossible.  The  best  practice  as  it  exists  at  present  can  only  min- 


ELECTROLYSIS  OF   UNDERGROUND  METAL  395 

imize  their  effect.  While  the  writer  has  no  desire  to  appear  as  an 
alarmist,  the  plain  facts  may  as  well  be  recognized  now  as  hereafter, 
when  the  particularly  dangerous  character  of  stray  electrical  cur- 
rents of  low  voltage  and  large  amperage  is  forcibly  presented  to  the 
public  in  the  sudden  collapse  of  some  important  structure  or  gas- 
and  water-supply  systems. 

It  is  a  false  reliance  that  masonry,  mortar,  concrete,  or  cement 
are  impervious  to  moisture  and  incapable  of  acting  as  an  electrolyte 
such  as  would  induce  electrolysis.  They  are  not  insulating  sub- 
stances, or  at  the  best  only  in  the  smallest  degree  under  the  most 
favorable  circumstances.  They  are  positively  porous  and  in  nearly 
every  case,  whether  tested  in  large  or  small  mass,  are  permeable  to 
all  waters  or  moisture  and  gases,  and  in  but  a  few  exceptional  cases 
ever  become  thoroughly  dry. 

*  A  number  of  electric-light  cable  conduits  in  Paris  were  constructed 
of  concrete,  particular  care  being  exercised  in  the  selection  of  the 
hydraulic  cement  and  sand  used,  as  well  as  the  ramming  of  it  into 
place.  The  conduits  were  far  above  the  water-line  of  the  city's  soil 
and  were  considered  to  be  water-tight.  The  copper  wires  soon 
became  covered  with  verdigris  and  copper  chloride  and  so  reduced 
in  area  that  grounding  and  heating  were  of  frequent  occurrence  from 
the  normal  currents  of  the  service.  A  number  of  minor  explosions  also 
occurred,  due  to  the  gases  formed  by  the  decomposition  of  salt 
water  that  filtered  through  the  cement  when  salt  was  strewn  on  the 
roadway  over  the  cable  conduit  to  melt  the  snow.  The  gaseous  mix- 
ture contained  oxygen,  hydrogen,  and  chlorine,  the  latter  gas  being 
due  to  the  chloride  of  sodium  in  the  salt  water.  The  leakage  of  the 
current  furnished  the  electrical  energy  to  decompose  the  salt  water 
and  fire  the  mixture,  also  to  form  the  carbonate  of  soda  and  caustic 
soda  that  was  deposited  upon  the  copper  wires. 

Earthenware  conduits  were  also  used,  but  were  not  water-tight, 
and  the  same  decomposition  of  the  salt  water  and  corrosion  of  the  cop- 
per wires  occurred  as  in  the  concrete  construction,  and  their  use  was 
soon  abandoned.  The  electric  cable  wires  are  now  taped  or  covered 
with  a  bituminous  compound  to  prevent  electrolytic  action. 

President  Learned,  in  his  inaugural  address  to  the  New  England 
Association  of  Gas  Engineers,  March  meeting,  1902,f  stated  that 


*  L' Electricien,  1892. 

f  "Electrolysis  of  Gas  Pipes."     American  Gas  Light  Journal,  March  3,  1902. 


396  ELECTROLYSIS  OF  NEW  ENGLAND   GAS  PIPES. 

the  conclusions  derived  from  a  large  number  of  tests  and  observations 
of  the  effect  of  electrolysis  on  the  gas-pipe  systems  in  a  number  of 
cities  in  New  England  were:  "  That  gas-pipes  laid  with  lead  joints 
have  15  per  cent  greater  resistance  to  electric  currents  than  water- 
pipes  of  the  same  diameter  with  similar  joints.  Screwed  joints  in 
wrought-iron  pipes  have  about  the  same  resistance  as  the  lead  joints 
in  cast-iron  pipes  of  the  same  diameter.  The  resistance  of  a  Port- 
land-cement joint,  as  ordinarily  made,  was  from  15,000  to  20,000 
times  the  resistance  of  a  lead-caulked  joint,  comparing  pipes  of  equal 
diameter.  That  the  resistance  of  the  cement  joint  depended  in  a  great 
measure  upon  the  amount  of  moisture  that  the  cement  takes  up  after 
setting. 

"  The  conclusions  drawn  from  the  experiments  made  on  gas-pipes 
of  all  diameters  laid  in  short  or  long  sections  were:  That  all  possible 
resistance  should  be  inserted  in  the  pipe  mains  by  making  the  joints 
of  some  insulating  or  semi-insulating  material,  with  an  asbestos  or 
tar-paper  ring  between  the  abutting  ends  of  the  pipe  in  order  to 
break  up  the  pipe-line  into  as  many  metallic  units  as  possible,  and 
isolate  them  from  all  other  pipe  or  trolley  systems,  so  far  as  practi- 
cable and  mechanical  conditions  would  allow.  The  pipes  should  be 
coated  with  a  water-proof  compound.  The  ordinary  foundry-dip 
coating  or  painting  with  oil-paints  had  no  appreciable  effect  to  delay 
or  diminish  electrolysis  of  the  pipes.  Neat  hydraulic  cement  cover- 
ings were  worthless  on  account  of  the  porous  nature  of  the  cement. 
It  absorbed  moisture,  was  inelastic,  and  easily  scaled  off  the  pipes  by 
frost  or  mechanical  injury. 

"  A  covering  made  from  3  parts  of  dry  clean  sand  and  2  parts  of 
coal-tar  boiled  to  a  pitch  at  660°  F.  made  a  mixture  that  was  slightly 
elastic  at  ordinary  temperatures,  was  thoroughly  water-proof  and 
when  applied  to  the  pipes  to  a  thickness  of  1J  inches,  had  an  insulat- 
ing resistance  of  over  1  million  of  ohms  to  the  cubic  inch.  A  short 
piece  of  2-inch  pipe  covered  with  this  mixture  and  immersed  in  a 
strong  solution  of  water  and  soda  ash  for  8  hours,  showed  no  signs 
of  the  absorption  of  any  of  the  solution,  nor  had  any  decrease  of 
electrical  resistance  been  developed." 

Mr.  Robert  Irvine,  F.C.S.,  reports  to  the  Chemical  Society  "that 
the  cause  of  many  disastrous  explosions  from  the  leakage  of  gas  had 
been  found  to  be  due  to  electrolysis  between  the  brass  unions  and 
other  composition  fittings  and  the  iron  service  pipes  and  casings  of 
the  meter.  Voltages  between  the  brass  and  iron  materials  ranged 


ELECTROLYSIS  OF  EAST  RIVER  SUSPENSION  BRIDGES.  397 

from  .3  to  .5  of  a  volt,  the  iron  in  all  cases  being  the  electro-positive 
metal/' 

The  corrosion  by  atmospheric  exposure  in  the  Brooklyn  Sus- 
pension Bridge  superstructure  is  deeply  seated  in  every  square  foot 
of  the  structure  and  is  beyond  correction  except  by  rebuilding  it.  It 
takes  a  corps  of  painters  constantly  at  work  three  years  to  paint 
the  structure,  and  the  coating  principally  serves  to  mask  the  corrosion. 
The  voltage  of  the  electrical  currents  passing  through  the  suspension 
cables  has  been  referred  to,  but  their  corrosive  effects  upon  the  an- 
chorage metal  from  the  inaccessibility  of  the  lower  ends  must  always 
be  a  conjecture.  These  parts  are  beyond  repair,  and  the  electrical 
currents,  whether  from  the  trolley  railway  on  the  bridge,  or  from 
the  scores  of  large  installations  surrounding  the  structure,  are  of 
large  amperage,  constant  and  uncontrollable  in  action.  That  they 
will  not  prove  active  agents  of  electrolysis  is  not  in  accordance  with 
past  experience. 

In  the  other  East  River  suspension  bridges,  where  steel  instead 
of  masonry  piers  are  used  to  carry  the  suspension  cables  and  the 
superstructure,  it  is  expected  that  the  large  metallic  contact  of  the 
wire  cables  at  the  top  of  the  steel  towers  will  form  a  short  circuit 
and  ground  for  any  electrical  energy  that  may  reach  them  from  the 
railway,  instead  of  using  the  anchorage  metal  for  a  terminal.  This 
theory  can  only  be  determined  after  the  bridge  railway  has  been 
put  in  operation.  The  many  points  of  junction  of  the  bridge  trestles 
with  the  masonry  piers  on  both  sides  of  the  river  may  divide  the 
trolley  currents  into  a  number  of  short  circuits  so  as,  in  a  measure,  to 
protect  the  structure.  But  this  cannot  prevent  the  currents  that 
come  to  the  anchorage  metal  from  the  installations  surrounding  them, 
from  using  the  cables  for  their  transmission,  as  they  provide  the 
best  and  shortest  metallic  path  for  their  ceaseless  circuit. 

A  further  fact  relative  to  the  electrolysis  of  the  anchorage  metal 
lies  in  its  condition,  even  before  any  material  strain  other  than  the 
weight  of  the  foot-path  cables  came  to  it.  In  the  Williamsburg 
Bridge,  the  anchorage  pits  were  carried  down  into  the  solid  rock  and 
near  if  not  below  the  water  level  of  the  river.  These  were  not  sealed 
water-tight  by  any  effectual  method  in  laying  the  superincumbent 
masonry.  The  anchorage  metal  was  put  in  place  under  a  continual 
seepage  of  brackish  water  or  that  rendered  alkaline  from  the -cement, 
more  or  less  pumping  being  required  during  the  work.  The  anchor- 
age metal,  also  the  forged  eyebars  for  the  cable  connections  were 


398  ELECTROLYSIS  IN  W1LL1AMSBURG  SUSPENSION  BRIDGE. 

indifferently  cleaned,  instead  of  being  sand-blasted,  and  were  painted 
with  Smith  &  Co.'s  "  Durable  Coating,"  the  advisability  of  apply- 
ing a  baked  japan  coating  being  disproved  on  account  of  its  cost. 

When  the  chain  of  eyebars  were  ready  for  the  cable  construction, 
an  anchorage  pit  was  pumped  dry  and  the  eyebars  inspected.  Though 
the  bars  were  covered  with  two  coats  of  "Durable  Coating,"  and  in 
place  only  about  two  years,  the  paint  was  nearly  destroyed,  and  corro- 
sion over  the  whole  surface  of  the  bars  wherever  the  water  had 
reached  them  was  virulent.  The  limited  room  in  the  pit  and  the  close 
association  of  the  eyebars  together  and  to  their  bed,  rendered  the 
cleaning  and  repainting  of  them  difficult  and  in  many  feet  of  their 
length  impossible.  A  new  coat  of  varnish  paint,  however,  was 
applied  in  the  damp  atmosphere  of  the  pit. 

For  the  future  protection  of  the  eyebars  it  is  proposed  that  when 
the  bridge  is  completed  and  the  chain  of  bars  are  bearing  their  load 
and  have  adjusted  themselves  to  their  permanent  position,  to  paint 
them  again  and  fill  in  between  and  around  them  for  a  foot  or  more 
with  melted  bitumen  and  to  fill  the  pit  with  concrete.  This  plan  does 
not  reach  the  anchorage  plates  and  metal  in  the  lower  end  and  inac- 
cessible part  of  the  pit.  The  corrosion  serpent  is  only  scotched  (not 
killed)  and  will  remain  inactive  for  but  a  short  time,  or  only  so  long  as 
the  concrete  remains  thoroughly  dry,  something  impossible  to  maintain. 

The  bitumen  coating  insulates  the  eyebars  so  far  as  it  can  be 
applied  and  passes  on  whatever  electrical  currents  may  reach  them 
from  any  source  to  the  lower  end  of  the  anchorage,  where  the  metal 
is  not  protected,  corrosion  in  progress,  and  inspection  almost  if  not 
quite  impossible.  To  think  that  electrolysis  will  not  take  place  in 
the  metal  at  both  ends  of  the  bridge  is  to  ignore  facts  already 
established.  Electrolysis,  or  even  corrosion  from  the  contact  of 
metal  with  moisture,  in  this  case,  is  not  the  sin  of  the  paint  manufac- 
turer; where  to  place  the  blame  is  not  hard  to  find. 

The  introduction  into  marine  service  of  appliances  for  the  genera- 
tion and  use  of  electric  power  and  light  has  developed  a  new  field  for 
electrolysis,  that  seriously  endangers  the  efficiency  and  life  of  all  vessels 
so  equipped.  An  examination  of  the  United  States  cruiser  Brooklyn, 
for  the  purpose  of  determining  the  effects  of  a  recent  grounding  of  the 
vessel,  has  revealed  the  fact  that  electrolysis  has  attacked  the  inner 
skin  or  false  bottom  of  the  ship,  and  it  is  in  such  an  advanced  state 
of  corrosion  as  to  be  practically  destroyed.  That  she  survived  the 
grounding  accident  is  a  cause  of  wonder  to  the  naval  officers. 


ELECTROLYSIS  IN  MARINE  CONSTRUCTION.  399 

Electrolysis  on  board  a  steel  ship  is  not  unlike  the  same  develop- 
ment by  direct  or  stray  electric  currents  in  land  or  underground  struc- 
tures. Wherever  a  current  of  any  potential  leaves  the  metal,  elec- 
trolysis is  the  result.  In  the  case  of  naval  vessels  there  is  an  enor- 
mous amperage  present  at  all  times  and  that  cannot  be  returned  to 
the  dynamos,  even  with  an  increased  capacity  of  the  return-current 
wires  over  those  employed  for  distribution  of  the  current. 

Divided  and  induced  currents,  also  the  electric  energy  developed 
by  corrosion  itself,  will  seek  their  own  course  either  in  returning  to 
the  dynamo  or  extinguishment  in  the  ground  connection.  The 
latter,  in  the  case  of  marine  work,  being  water  saline  or  foul  in  char- 
acter, is  a  more  efficient  electrolyte  than  any  earthy  substance. 
Hence  electrolysis  in  marine  constructions  willl  naturally  be  more 
rapid  and  virulent  than  on  a  similar  ferric  area  and  current  exposure 
on  land  or  in  underground  structures. 

As  before  stated,  no  paint  or  plastic  coatings  of  the  metal  will 
prevent  electrolysis.  At  best  they  may  temporarily  mask  its  progress, 
but  it  only  requires  a  short  time  or  a  slight  change  in  the  conditions 
to  reveal  it. 

Corrosion  or  electrolysis  of  marine  metal  can  only  be  controlled 
by  the  use  of  some  alloy  of  steel  that  will  minimize  the  action,  and 
by  such  an  increase  in  the  thickness  of  the  parts  of  the  ship  exposed 
to  corrosive  influences  as  will  for  a  time  provide  for  any  reduction 
of  strength  in  the  corroded  parts  or  alloyed  metal;  also  by  a  plan  of 
construction  that  recognizes  the  possibility  of  the  evil  and  provides 
that  corroded  members  can  be  removed  without  practically  rebuild- 
ing the  ship.  (See  page  339  for  Dr.  Wurtz's  protective  method.) 

Insulation  of  motors  and  their  connections  and  the  positive  pro- 
hibition of  the  connection  of  any  electric  current,  even  of  the  smallest 
amount,  to  any  part  of  the  structure  will  reduce  but  not  prevent 
the  dangers  of  electrolysis,  whether  in  marine  or  land  constructions. 

In  either  case,  constant  and  thorough  inspection  of  all  ferric 
surfaces  by  an  inspector  who  knows  what  to  look  for,  and  is  compe- 
tent to  recognize  it  when  it  is  found,  is  an  essential.  Even  if  the 
inspector  cannot  avert  corrosion  when  found,  at  least  the  danger 
can  be  noted,  watched,  and  a  warning  given  when  it  is  time  to  desert 
the  ship.  All  of  these  essentials  appear  to  have  been  absent  in  the 
case  of  the  cruiser  Brooklyn,  and  probably  they  are  also  neglected 
in  all  of  the  steel  vessels  in  commission. 


CHAPTER  XXXV. 

ANTI-CORROSIVE    MARINE    PAINTS    AND    ALLOYS. 

THE  so-called  marine  paints  are  those  applied  to  ships'  bottoms 
to  prevent  corrosion,  also  those  to  prevent  the  growth  of  marine 
plants,  barnacles,  etc.,  and  known  as  anti-corrosive  and  anti-fouling 
paints.  The  anti-corrosive  marine  paint  is  not  applicable  to  ferric 
bodies  in  any  other  place  than  under  water,  as  in  the  air  they  crack, 
flake,  or  crumble  off  rapidly.  They  draw  the  necessary  oxygen  to 
dry  them  from  the  water  and  carry  large  quantities  of  metallic  salts 
and  volatile  driers  to  enable  them  to  harden  in  an  hour  or  so,  an 
indispensable  quality  in  a  paint  for  a  ship's  bottom.  One  of  the 
earliest  patents  in  the  arts  was  issued  in  1670  for  a  tar  and  asphalt 
varnish  for  ships'  bottoms,  and  since  that  time  patents  for  marine 
paints  have  been  issued,  experiments  and  extended  applications  of 
them  have  been  made  by  the  thousand,  and  yet  neither  the  corro- 
sion nor  the  fouling  of  ships'  metal  has  been  rendered  materially 
less  than  it  was  a  hundred  years  ago. 

Fossil  resin  varnishes  prove  to  be  the  best  vehicles  for  marine 
paints,  whatever  the  composition  of  the  pigments  assembled  with 
them.  The  nature  of  the  pigments  in  these  paints  has  a  governing 
influence  in  exciting  the  galvanic  action  between  themselves  and 
the  ship's  metal,  which  action  is  speedily  fatal  to  the  coating  as  well 
as  rapidly  increasing  the  corrosion. 

Corrosion  in  marine  constructions  is  not  only  increased  by  the 
action  of  sea-water  on  the  pigments  and  covered  metal,  but  by  the 
great  porosity  of  the  paints  on  account  of  the  quantity  of  volatiles 
used.  This  porosity  of  the  coating  is  also  a  prime  factor  in  the  decay 
of  paint  on  land  structures.* 

The  following  tabulated  results  of  a  test  of  a  large  number  of  anti- 
corrosive  coatings  exposed  to  sea-water  shows  how  inefficient  nearly 
all  of  them  are  to  meet  the  requirements  of  marine  exposures.  The 
baked  coatings,  Nos.  158,  159,  174,  175,  35,  113,  104,  105,  122, 
124,  not  being  applicable  for  a  ship's  bottom,  however  effective  they 

*  Pages  405,  406,  407. 

400 


MARINE  ANTI-CORROSIVE  COATINGS.  401 

may  be  for  many  other  marine  purposes,  are  practically  eliminated 
for  comparison  with  the  other  marine  paints;  but  are  useful  to  com- 
pare with  the  other  coatings  if  used  on  land  exposures  where  the 
corrosive  influences  are  not  so  severe.  Porosity  in  the  baked  coat- 
ings is  eliminated  and  corrosion  lessened  whether  the  coatings  are 
used  on  land  or  for  sea-water  exposure. 

The  Kauri  and  Zanzibar  varnishes,  composed  of  20-30  or  40 
gallons  of  linseed-oil  to  100  pounds  of  fossil  resin,  were  not  as  effec- 
tive for  preventing  corrosion  as  where  a  pigment  was  added 
to  the  same  quality  of  varnish,  the  order  of  merit  for  the  pigments 
so  used  being  carbon,  zinc  oxide,  graphite,  red  lead,  and  iron  oxide. 

The  test,  while  of  value  as  a  record  of  the  comparative  merits  of 
the  several  coatings  to  resist  corrosion,  when  exposed  on  a  small  plate 
to  sea-water  under  absolutely  uniform  conditions  for  all  of  the  coat- 
ings, still  lacks  the  factor  of  their  behavior  when  applied  in  mass  of 
material  to  a  ship  or  to  land  structures  exposed  to  sea-air  or  sea- 
water. 

The  corrosion  in  the  aluminum  plates  indicates  that  the  metal 
to  be  non-corrosive  must  be  alloyed  with  a  metal  lower  in  the  electro- 
chemical scale  than  copper,  in  order  to  render  aluminum  of  any 
practical  value  for  constructions  of  any  magnitude  where  strength 
or  permanency  are  required. 

See  Mr.  R.  P.  Hobson's  (naval  constructor,  U.  S.  Navy)  report 
to  the  U.  S.  Navy  Department  "On  the  Uses  of  Aluminum  for  Naval 
Work,"  published  by  the  Navy  Department,  Washington,  D.  C.,  for 
other  data  on  the  corrosion  of  aluminum. 

In  some  experiments  of  the  "Alloys  Research  Committee"  by 
Prof.  Roberts- Austen,  F.R.S.,  "samples  of  alloys  containing  40  to 
60  per  cent  of  aluminum  were  kept  a  number  of  months  before  being 
analyzed.  During  this  period  they  had  spontaneously  disintegrated 
to  a  powder.  The  powder  was  not  oxidized,  but  consisted  of  clean 
metallic  grains,  probably  resulting  from  chemical  changes  which  had 
taken  place  in  the  solid  alloys.  Whether  the  iron  and  aluminum  were 
in  a  state  of  solution,  or  were  chemically  combined  when  molten, 
they  are  evidently  chemically  combined  in  the  metallic  powder  as 
attempts  to  melt  it  are  unsuccessful,  which  indicates  the  formation  of 
an  infusible  compound.  The  two  metals  may  have  been  too  hot  to 
unite  thoroughly  when  in  a  molten  state,  but  a  long-continued 
proximity  at  a  lower  temperature  affected  their  chemical  union." 

M.  Le  Chatalier,  in  a  paper  read  before  the  Academie  de  Sciences, 


402  CORROSION  OF  FERRIC  ALLOYS. 

Paris,  stated  that  equal  parts  of  aluminum  and  copper  were  fused 
together  in  a  crucible.  The  ingot  was  placed  in  a  solution  of  common 
salt  and  lead  chloride  for  twenty -four  hours  with  a  view  of  dissolving 
out  the  uncombined  aluminum .  No  change  in  the  ingot  was  apparent  at 
the  end  of  this  time.  The  ingot  was  removed  from  the  bath,  washed, 
and  dried.  Twelve  hours  afterwards  the  ingot  was  found  to  be 
reduced  to  powder  from  the  spontaneous  oxidation  cf  the  alloy.  A 
similar  ingot  not  immersed  in  the  saline  bath  was  unchanged  at  the 
end  of  a  month. 

Three  small  aluminum  boats,  used  by  Mr.  Wellman  in  his  1894 
polar  expedition,  soon  after  they  were  brought  back  could  be  crum- 
bled in  the  hand. 

Corrosion  of  Ferric  Alloys. 

The  influence  of  copper  and  nickel  alloyed  with  wrought  iron  and 
soft  steel  was  made  the  basis  of  a  paper  by  Mr.  F.  H.  Williams,  C.E., 
read  before  the  Engineering  Association  of  Western  Pennsylvania. 
The  paper  was  based  upon  experiments  made  in  the  line  of 
some  recent  investigations  by  Mr.  H.  M.  Howe,  as  given  in  his  paper, 
"Relative  Corrosion  of  Wrought  Iron  and  Soft  Steel  and  Nickel 
Steel,"  read  before  the  International  Congress,  Paris,  on  Testing 
Materials.* 

"In  prosecuting  the  tests,  Mr.  Williams  selected  four  samples  of 
steel,  viz.:  A,  an  ordinary  soft  Bessemer  steel;  B,  C,  D,  soft  Besse- 
mer steels  to  which  copper  had  been  added  in  the  converter  so  that 
they  contained  respectively  0.078,  0.145,  0.263  per  cent.  In  addi- 
tion, another  set  of  test  materials,  consisting  of  one  soft  Bessemer- 
steel  sample  and  four  of  wrought  iron,  were  similarly  alloyed,  sample 
number  4  of  wrought  iron  having  0.393  per  cent  of  copper.  All 
the  samples  were  brought  to  the  same  dimensions,  then  weighed 
and  suspended  in  a  frame,  so  that  they  could  all  be  dipped  simul- 
taneously in  water  and  left  to  dry  in  the  open  air,  this  treatment 
being  repeated  frequently  each  day  for  a  month.  The  daily  increase 
in  weight  due  to  oxidation  was  small,  but  of  such  a  persistent  char- 
acter as  to  indicate  the  retarding  influences  of  the  copper  upon  the 
corrosion.  Finally,  where  there  appeared  a  tendency  of  the  oxide 
to  scale  off,  the  treatment  was  suspended,  the  samples  dried,  cleaned 
from  all  oxide,  and  weighed.  The  loss  in  the  original  weight  of  the 
samples  is  tabulated,  viz.: 

*  Engineering  Record,  December  1,  1900,  p.  519. 


CORROSION  OF  FERRIC  ALLOYS.  403 

Loss  FROM  ONE  MONTH'S  EXPOSURE  TO  ATMOSPHERIC  CORROSION. 

A.  Soft  Bessemer  steel 1 . 85  per  cent. 

B.  "  "  "     with  0.078%  copper 0.89 

C.  "  "  "        "     0.145%       "     0.75 

D.  "  "  "        "     0.263%       "     0.74        " 

Soft  Bessemer  steel,  second  sample 1 . 65        " 

Wrought-iron  sample  number  1  with  0.078%  copper 0.76        " 

"  "  "       2      "    0.145%      "       0.80        " 

"  "       3      "    0.263%      "       0.87 

«  "  "       4      "    0.393%      " 0.53        " 

"  Mr.  Howe's  experiments  indicated  that  in  large  plates  of  metal 
containing  nickel  in  approximately  the  same  proportions  as  the  above 
examples,  and  exposed  for  a  considerable  time,  the  corrosion  was  simi- 
larly retarded.  The  introduction  of  a  small  amount  of  copper  or 
nickel  into  soft  steel  can  be  easily  effected,  and  their  presence  within 
the  amount  necessary  to  obtain  the  above  results  has  been  demon- 
strated not  to  be  prejudicial  to  its  physical  properties.  The  data 
here  presented,  while  not  showing  that  corrosion  of  ferric  bodies  can 
be  wholly  prevented  by  alloying  them  with  copper  or  nickel,  they 
do  indicate  that  a  soft  steel  can  be  made  capable  of  resisting  corrosion 
quite  as  well  as  wrought  iron  and  thus  settle  the  debate  about  their 
relative  corrosibility  now  so  much  in  question." 

In  the  case  of  aluminum,  the  natural  field  for  its  use  appears  to 
be  in  marine  construction,  where  lightness  is  an  essential  requirement, 
particularly  in  naval  construction,  where  economy  in  weight  has  a 
vital  relation  to  military  efficiency.  But  its  corrosibility,  if  exposed 
to  sea-air  or  sea-water,  has  demonstrated  its  unfitness  for  any  struc- 
ture exposed  to  these  influences. 

Alloys  of  copper  with  aluminum  increase  the  corrosion,  which  is 
greater  as  the  amount  of  copper  is  increased.  With  2  per  cent  of 
copper  the  increase  of  corrosion  is  markedly  greater  than  with  the 
pure  aluminum,  and  where  5  per  cent  of  copper  is  used,  as  in  the 
case  of  the  Yarrow  torpedo-boats,  on  account  of  the  great  increase 
in  the  strength  of  the  metal,  the  corrosive  effects  were  disastrous,  and 
caused  an  abandonment  of  the  metal  for  French  naval  work.  The 
interest  in  this  feature  is  special,  as  the  aluminum  needs  an  alloy  to 
increase  its  strength,  and  copper  appears  to  be  the  one  metal  best 
suited  for  this  purpose,  though  other  metals  are  available.  The 
increased  corrosion  due  to  the  presence  of  copper  is  attributed  to 
the  fact  that  the  two  metals  are  so  widely  separated  in  the  electro- 
chemical scale  that  an  alloy  made  from  them  contains  the  necessary 


404  ACTION  OF  SEA-WATER  ON  METALS. 

elements  for  a  strong  galvanic  action  that  soon  destroys  the  integrity 
of  the  metal.  This  action  is  also  developed  where  copper  in  any 
form  is  brought  into  contact  with  iron  or  steel  for  any  exposure. 

The  action  of  sea-water  on  the  corrosion  of  various  metals  has  been 
investigated  by  the  German  engineer,  Digel,  who  reports  "that  alloys 
of  copper  20  per  cent  and  nickel  42  per  cent  are  not  very  rapidly 
corroded.  Adjacent  masses  of  iron,  copper,  or  copper  alloys  render 
the  copper  and  nickel  alloys  somewhat  immune  against  sea-water 
corrosion,  the  above-mentioned  metals  being  rapidly  corroded. 

"  Copper  and  zinc  alloys  are  corroded  almost  uniformly  over  the 
surfaces  exposed  to  the  sea-water.  When  the  zinc  exceeds  24  per 
cent  of  the  alloy,  it  is  leached  out,  leaving  a  brittle  porous  mass  of 
copper.  Adding  15  per  cent  of  nickel  to  the  alloy  prevents  this 
leaching  action. 

"  Very  pure  electrolytic  copper,  in  contact  with  ordinary  com- 
mercial copper  (99  per  cent  pure),  is  very  rapidly  corroded  by  sea- 
water.  When  the  two  coppers  are  not  in  contact,  they  corrode  about 
alike.  Both  of  the  above  brands  of  copper  when  annealed  are  more 
rapidly  corroded  than  when  rolled.  Copper  coated  with  zinc  is 
temporarily  protected  from  sea-water,  but  when  the  zinc  has  been 
dissolved,  the  corrosion  of  the  copper  is  increased  rapidly. 

"  Electrolytic  copper  that  had  its  surface  oxidized  in  places  devel- 
oped rapid  galvanic  action  in  the  clean  spots.  Copper  pipes  brazed 
into  vessels  or  into  each  other  are  subject  to  corrosion  in  the  brazed 
joints  from  galvanic  action. 

"  One-half  of  1  per  cent  (0.5)  of  arsenic  in  metal  greatly  retards 
corrosion. 

"Wrought  iron  and  steel  of  various  methods  of  manufacture  are 
greatly  influenced  in  corrosibility  by  the  amount  of  phosphorus 
contained  in  them.  With  1  per  cent  of  phosphorus  present  the  corro- 
sion was  a  little  over  one-half  as  great  as  in  the  case  where  the  iron 
was  free  from  phosphorus.  When  two  pieces  of  phosphorus  iron 
or  steel  were  in  contact,  the  sea-water  corroded  the  low  phosphorus 
metal  from  two  to  five  times  as  fast  as  the  high-grade  metal. 

"  Iron  alloyed  with  nickel  showed  the  same  behavior. 

"  The  normal  corrosion  of  single  plates  of  metal  was  less  as  the 
percentage  of  nickel  increased.  When  two  plates  differing  in  the 
contained  nickel  were  brought  into  contact,  the  plate  higher  in  nickel 
was  almost  completely  protected  from  corrosion." 


MARINE  PAINT  TEST. 


405 


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MARINE  PAINT   TEST. 


407 


CHAPTER  XXXVI. 


MISCELLANEOUS     TABLES     AND     DATA. 
PIGMENTS  AND  INERT  SUBSTANCES. 


Substance. 

Symbol. 

Specific  Gravity. 

Asphaltum.  .        

1  .  8  —  1  .  39—1  .  04 

Alumina  oxide  (clay)  

A1O 

2.75—2.6 

Anthracite  coal  

1.70—1.35 

Bituminous  coal  

1.318—1.277 

Bitumen 

1.16  —  o.83 

Barytes  (heavy  spar).  . 

BaSO4 

4.7  —  4.3 

Brick-dust                                    

1.50  —  i  30 

Cement,  hydraulic,  common  

1.6—1.5 

"             "           Portland  

1.51—1.25 

Rosendale  

1.00—0.96 

Charcoal  in  bulk 

c 

0  441 

"            oak 

« 

0.336  —  0  331 

Coke  natural  Virginia.                  .    .    . 

ii 

0.746 

"      hard  foundry.  .              .... 

ii 

0.800 

"      gas  retort  

n 

0.70 

Cobalt  (blue)  

8.6  —  8.5 

Coal-tar  (gas  retort)  

1.1  —  1.00 

Chalk,  red  and  black  

CaO 

2.8—2.2 

"       whiting,  Spanish  white  

2  .  l  —  l  .  g 

Clay  (see  Terra-Alba)  

2.71  —  2.56  —  1.93 

Carbon  (diamond) 

c 

3  529  —  3  55 

Feldspar  

2.8—2.5 

Flint 

1  93 

Gneiss  and  granite 

2.8—2  76—2  62 

Glass 

2.782  —  2  5 

Graphite  amorphous  .  . 

2.768  —  2  208 

"       flake  or  foliated. 

1.40—1.21 

Gypsum,  native  sulphate  of  lime  (hydrated)  . 
(calcined)  plaster  of  Paris 

CaOSO3  +  H2O 
CaOSO, 

2.5—2.38 
2  .  4  —  2  .  08 

Lampblack  

C 

0  .  44  —  0  .  80 

Lime  (quick)  ....                         .    .            .    . 

CaO 

0  .  88—0  .  8 

Limestone,  common  gray.  .       .        .... 

CaCO, 

2.7—2.6 

Carrara  marble  

n 

2.717 

Lead,  metallic  

Pb 

11.44  —  11.07 

"      white,  carbonate  

PbCO3 

6  .  480  —  6  .  465 

"      chromate  

PbCrO3 

5  .  2  —  4  .  61 

"      hydrate..  . 

Pb(OH)2 

7  00  —  6  6 

sublimed.  .   . 

PbSO4 

6  258 

sulphite  (dark  color). 

PbS 

6.43 

"      sulphate  (white  color) 

PbSO4 

7.13 

Litharge.  . 

PbO 

9.00—8.50 

408 


PIGMENTS  AND   INERT  SUBSTANCES. 
PIGMENTS  AND  INERT  SUBSTANCES — Continued. 


409 


Substance. 

Symbol. 

Specific  Gravity. 

Lithopone  (zinc  sulphate).  . 

PbS04 
Pb304 

4.2 
9.07—8.94—8.06 
2.4—1.73 
3.1-2.75 
2.0—1.79 
3.2—2.72—2.4 
4.97—4.816 
4.6-3.2 
7.84—7.77 
5.77 
5.334.62 
4.20—3.80 

6.062 

3.5—3.8 
1.152 
2.7—2.64 
1.089—1.07 
8.1—7.5 
1.76—1.44 
2.8—2.5—1.9 
2.34—1.9 
2.8—2.3—1.8 
2.9—2.7 
3.6—4.3 
2.8—2.65 
5.175.04 
2.03—3—2.05 
2.2—2.1 
2.4—2.2 
2.71—2.56 
2.4—1.92 
8.91-8.1 
7.5—7.0 
7.0 
4.4—4.0 
5.6—5.4 
4.2—3.9 
5.3—5.0 

Marl                      

MgC02 
MnO 

Oclire                                

Iron  metallic  

Fe 

Fe203 

•       Fe,0,      1 

Fe304      J 
Ca4(P04)2 

'  '     oxide  (red  rust)  ,  70%  iron,  30%  oxygen. 
Iron  ore,  red  and  brown;   hematite,  specular 
and  columnar"  spathic  etc  

Black     magnetic     oxide,      72.413%      iron, 
27  587%  oxygen  

Phosphate  of  lime  (basic  steel  furnace  slag)  .  . 
Pitch 

(C^A). 

Orange  or  Paris  red   

Silica  (crystalline)  

SiSO2 
SiS02 

"      (amorphous)  

Silex  (floated)     

Slate                                .    . 

Sulphate  of  iron  (copperas).  . 

Fe3S04 

S 

Sulphur,  native  ore,  melts  at  115°  to  120°  F.  . 

Umber  (argillaceous  brown  hematite  iron  ore)  . 
Terra  alba,  China,  pipe   and   potters'   clay, 
complex  oxides  of  all  metals  

2Fe8O3,SiO2  +  H2O 
HgS 

Vermilion  (mercuric  sulphate)  

Vermilionette  (mixed  color)  

Zinc  metallic  

Zn 
ZnCO3 
ZnO 

ZnS 
ZnSO, 

"    carbonate  

"   oxide  or  zinc  white  

"    sulphide  (dark  color)  

"    sulphate  (white  color)..  . 

The  trade  or  commercial  color  pigments  number  245,  viz. : 


Black 22 

Blue c 28 

Brown 24 

Gray... 3 

77 


Green 46 

Red 50 

White 36 

Yellow 36 

168 


410  PIGMENTS.    METALLIC  BASES 

CHARACTERISTICS  OF  METALLIC  BASES  OF  PIGMENTS. 


Metal. 

Symbol. 

Combining 
Weight. 

Specific  Gravity. 

Antimony   

Sb 

120.4 

6.86—6.36 

Al 

27.1 

2.71—2.56 

As 

75.1 

5.96—5.52 

Ba 

137.4 

6.85 

Bismuth  '.  

Bi 

j      200.0  ) 

9.90—9.74 

Ca 

"1      208.1  j 
40  1 

1.58 

Cobalt  

Co 

59 

8  .  6  —  8  .  5 

CoDper.  .  . 

Cu 

63  6 

8.92  —  8.69 

Iron     

Fe 

56. 

7.77 

Lead  

Pb 

206.9 

11.38 

Magnesium  

Mg 

12. 

1.743 

Mn 

55. 

4.97  —  4.82 

Mercury                       . 

Hg 

200 

13  62  —  13  58 

Nickel 

N! 

58  3 

8  93  —  §  28 

Potassium  .    . 

K 

39 

0  865 

Phosphorus  

p 

31 

1  £23  —  1  777 

Silicon         

Si 

28  4 

2  8-2  5 

Sodium  

Na 

23 

s 

32  1 

2  05  —  2  033 

Gold  

Au 

197  2 

19  36  —  19  245 

Silver  

Ag 

107  7 

10  51  —  10  474 

Tin  

Sa 

119-117  8 

7  409-7  300 

Zinc  

Zn 

65  4 

7  13  —  7  0 

Red  and    brown  hematite  and  specular 
iron  ore;   iron  =70%;   oxygen  =30%.. 

Magnetic  or  black  oxide  of  iron;    iron= 
72413%;   oxygen  =  27.587%  . 

Fe203 
Fe,(X 

56  and  16 
56  and  16 

5.4-5.3 
4.65-4.2 

5  6  —  5  3 

ELEMENTS   THAT  CAUSE  THE  DECAY  OF  PAINT.        411 


Gases  and  Elements  that  Cause  the  Decay  of  Paint. 

The  principal  gases  and  elements  that  affect  all  paints  at  a  tem- 
perature of  60°  F.  and  under  one  atmospheric  pressure  are: 


Substances,  Gas  or  Vapor. 

Specific 
Gravity. 

Number  of  Cubic  Feet 
per  Pound. 

Alcoholic  vapor                    

1.589 
0.597 
1.00 
1.0236 
2.7 
2.6447 
0.9727 
1.529 
0.9784 
0.302 
0.54 
0.9714 
1.056 

0.06926 
0.559 

0.49959 
0.622 
2.76 
0.102 
0.105 
0.09 
2.213 
0.177 
2.586 
0.812 

8.27 
20.95 
13.11—13.14 
12.80—12.831 
4.78 
4.85 
13.57—13.60 
8.594 
12.580 
33.112 
24.335 
12.752 
11.887 

189.552—189.70 
23.479 

26.36 
21.077 
4.76 

5.90 

74.422 
5.08 
boils  at  140°  to  150°  F. 

Ammonia.      "     NH3  ..   

"    saturated  as  fog  at  80°  F.... 
Benzine  vapor  C6H6  

Bisulphide  of  carbon,  CS2  

Carbonic-acid  gas  CO2  

Ethelene  or  olefiaiit  gas,  C2H4  

Natural  gas                               

Oxygen,  O  .            

Hydrogen,  H,  16  times  lighter  than  air          | 
14|     "                     "     oxygen  f 

Phosphoric  acid,  3HOPO6 
Phosphorated  hydrogen,  PH3 
Steam   saturated   212°  F  

"      "  coke                     

"      "  wood     .  .              

Wood-alcohol  vapor,  CH4O2  

Oxygen  in  Pigments. 

Paint-trade  literature  bears  so  persistently  upon  the  point  that 
red  lead,  from  the  great  amount  of  oxygen  it  contains  is  not  only 
self-destructive,  but  will  destroy  all  other  paints  of  which  it  forms  a 
part;  also,  that  by  reason  of  this  inherent  element,  it  acts  the  part 
of  a  carrier  for  an  additional  amount  of  oxygen  that  it  may  collect 
from  other  sources,  the  joint  effect  resulting  in  an  early  destruction 
of  the  coating;  also  in  promoting  corrosion  of  the  covered  surfaces. 
The  following  comparison  of  the  amount  of  oxygen  in  a  number  of 
pigments  and  so-called  inert  substances  in  common  use  in  paints  is 
of  interest  upon  this  point: 


412 


OXYGEN  IN  PIGMENTS. 


Substance. 

Symbol. 

Metallic, 
Per  Cent. 

Oxygen, 
Per  Cent. 

Other  Elements, 
Per  Cent. 

PbO 

92.822 

7.178 

T>pfl   lpnfl 

Pb3O4 

90  63 

9  37 

^Vhitf*  IPQH  fpflrfoonatG^ 

PbCO, 

77  516 

17  987 

Carbon        4  4Q7 

Rnhlimafpci  lead 

PbSO4 

71.831 

18  561 

Sulphur     9  608 

Sulphate  of  lead  (native  ore)  .  . 
"         "    "       (pigment).  .  . 
Sulphite  of  lead  

PbS03 
PbS04 
PbS 

72.09 
62.283 
86.57 

16.746 
21.145 
00.00 

11.164 
10.572 
13  43 

Zinc  oxide                        

ZnO 

80  344 

19  656 

*'    sulphide                   

ZnS 

67  077 

00  00 

32  923 

"   sulphate  ....            

ZnSO4 

40  495 

39  670 

19  835 

"   carbonate  .                .... 

ZnCO3 

52  153 

38  278 

Carbon,     9  569 

Whiting  chalk.  .                   .... 

CaO 

71  479 

28  52 

Iron  oxide                            

Fe,O, 

70  00 

30  00 

"   magnetic  oxide  

FeoO. 

72  413 

27  587 

Barytes  

BaSO4 

65  172 

22  097 

Sulphur,  12.731 

Gypsum           

CaOSO3 

41  20 

35  28 

"        23  .  52 

Manganese  dioxide  (pyrolusite)  . 
Vermilion                                   •  • 

MnO2 
HgS 

43.161 
86  207 

56.839 
00  00 

"         13  793 

Umber  (hydrated)                     j 

2Fe2O3.SiO2 

-I-H2O 

55  .  735 

34.67 

Silicon,      9  .  594 

COMBINATIONS  OF  OXYGEN  WITH  CARBON  AND  SULPHUR. 


Substance. 

Symbol. 

Oxygen, 
Per  Cent. 

Carbon, 
Per  Cent. 

Number  of 
Cubic  P^eet 
of  Gas  in 
One  Pound. 

Carbonic  oxide 

CO 

57    14 

42  86 

13  57 

Carbonic  acid 

CO, 

72  73 

27  27 

8  59 

Carbon  trioxide. 

CO, 

80  00 

20  00 

6  47 

Sulphuric  oxide.            

SO 

33  264 

Sulphur. 
67  736 

Sulphurous    acid    (the    acid    of 
burning  sulphur) 

SO2 

50  00 

50  00 

3  848 

Sulphuric  acid 

so, 

60  00 

40  00 

3  569 

"            "     anhydrous.  .  .  . 

so! 

66  6 

33  4 

2  944 

CHANGES  IN  PIGMENTS  DUE  TO  ATMOSPHERIC  INFLUENCES. 

Red  lead  (Pb3O4)  =  lead,  90.63  per  cent;    oxygen,  9.37  per  cent. 
Specific  gravity,  9.07.     682  grammes,  volume=75.2  c.c. 

Upon  exposure  to  hydric-sulphide  gas  in  the  atmosphere  it 

Changes  to 

Red-lead  sulphide  (PbS)  =  lead,  86.61  per  cent;  sulphur,  13.39  per  cent. 
Specific  gravity,  7.13.     714  grammes,  volume=  100.1  c.c. 
Increase  in  volume,  24.9  per  cent. 


CHANGES  IN  PIGMENTS.  413 

Zinc  oxide  (ZnO)  =  zinc,  80.344  per  cent;  oxygen,  19.656  per  cent. 
Specific  gravity,  5.42.     81  grammes,  volume=14.9. 

Upon  external  atmospheric  exposure,  absorbs  carbonic  acid  and 
Changes  to 

Zinc  carbonate  (ZnC03)  =  zinc,  52.153  per  cent;  j  °Xyugen'  38'278  per  cent' 

(  carbon,     9.569  per  cent. 

Specific  gravity,  4.44.     125  grammes,  volume=28. 
Increase  in  volume  nearly  double. 

White  lead  (PbCO3)  =  lead,  77.516  per  cent;    j  oxygen,  17.987  per  cent; 
Hydrated  carbonate;  (  carbon,     4.4972  per  cent. 

Specific  gravity,  6.480. 

Absorbs  carbonic  acid  from  the  atmosphere  and 
Changes  to 

Subcarbonate  of  lead  (PbCO4)  =  lead,  73.138  per  cent;    j  °XyKgen'  20'62  Per  centJ 

'    (  carbon,     6.242percent. 

Specific  gravity,  6.40. 

Absorbs  sulphurous-acid  gas  and 

Changes  to 
Sulphide  of  lead  (PbS)  =  lead,  86.57  per  cent;  sulphur,  13.43  per  cent. 

(Dark  color.) 
Specific  gravity,  6.45. 

Absorbs  more  sulphurous  acid  and 

Changes  to 

Sulphate  of  lead  (PbSO4)  =  lead,  68.283  per  cent;    j  oxygen,  10.572  per  cent; 
(Light  color.)  (  sulphur,  21. 145  per  cent. 

Specific  gravity,  7.13. 

Barytes  (heavy  spar)  (BaSO4)  =  Ba,  65.172  per  cent;  j  oxygen,  22.097  per  cent; 
Native  sulphate  of  barium;  (  sulphur,  12.736  per  cent. 

Specific  gravity,  4.7  to  4.3. 

Absorbs  carbonic  acid  from  the  atmosphere,  that  releases  the 
one  atom  of  sulphuric  acid  (S03)  in  its  composition  and 
Changes  to 

Barytes  carbonate  (BaCO3)  -  Ba,  69.10  per  cent;    j  oxyf n'  ^'\\  Per  cent' 

(  carbon,     6.18  per  cent. 

Specific  gravity,  4.1.     Change  in  volume,  5  per  cent. 

Gypsum  (native)  )  c  =  5  oxygen,  35.28  per  cent; 

Sulphate  of  lime  J  (sulphur,  23.52  per  cent. 

Specific  gravity,  2.4  to  2.08  (calcined). 

When  calcined,  it  releases  sulphuric  acid  and  absorbs  carbonic 
acid  from  the  atmosphere  and 

Changes  to 

Carbonate  of  lime  >CaO=  calcium,  71.478  per  cent;  oxygen,  moisture  and  car- 
Chalk  or  whiting     j"         bonic  acid,  28.522  per  cent. 

Specific  gravity,  2.2  to  2.8.     Increase  in  volume,  5  per  cent. 


414 


CORROSIVE  ELEMENTS  IN  OILS. 


Corrosion  of  Metals  by  Oil. 

Experiments  to  determine  the  action  of  oils  upon  copper  and 
iron  plates  ten  square  feet  resulted,  viz.: 


All  Pure  Oils. 

10-Days'  Ex- 
posure on 
Copper. 
Gain  in  Weight. 
Grains. 

24-Days'  Ex- 
posure on  Iron. 
Gain  in  Weight. 
Grains. 

Almond. 

0   103 

0  0040 

Colza  

0.017 

0.08 

Castor 

0  010 

0  0048 

Lard  

0.013 

0.025 

Linseed,  raw  
Neat's-foot  
Olive  

0.30 
0.11 
0  22 

0.005 
0.0875 
0  0062 

Paraffin  

0.0015 

0  0045 

Seal  

0  .  0485 

0.005 

Sperm  

0.003 

0.046 

The  result  shows  that  the  action  of  any  oil  upon  any  one  metal  is 
no  guide  to  the  degree  that  it  will  affect  another  metal,  but  that  all 
metals  are  affected  by  oil  to  some  degree.  (W.  H.  Watson.) 

In  other  experiments  upon  commercial  linseed-oils  made  from 
unripe  seeds  by  the  steam  and  dioxide-of -carbon  processes,  also  of 
sulphuric-acid  cleared  oils  and  petroleum  oils  containing  traces  of 
sulphur,  the  corrosive  action  was  from  two  to  three  times  the  above 
amounts  on  both  the  copper  and  iron. 

The  corrosive  effects  of  oils  in  contact  with  different  metals  at 
ordinary  summer  temperatures,  are  as  follows: 


Oils. 

Metals  Not 
Attacked. 

Metals  Least 
Attacked. 

Metals  Most 
Attacked. 

Mineral.  . 

Zinc  and  copt 

>er 

Bronze 

Lead 

Olive  

U             U                 (( 

Tin 

CoDoer 

Colza  

Bronze  and  t 

in 

Iron 

£p 

Tallow 

( 

Tin 

tt 

Lard  

t  . 

Zinc 

ft 

Cottonseed 

t 

Lead 

Tin 

Spermaceti. 

i 

Bronze 

Zinc 

Seal.  . 

t 

Bronze 

Copper 

Whale  

Tin 

Bronze 

Lead 

CORROSIVE  ELEMENTS  IN  SNOW   WATER. 


415 


ANALYSIS    OF    SAMPLES    OF  MELTED   SNOW  FROM  A  NUMBER    OF  LOCALITIES, 
SHOWING  CORROSIVE  INGREDIENTS.     (PROF.  VIVIAN  B.  LEWES,  PH.D.) 

Carbon  (soot) 39 . 00  per  cent  1  51 . 30  per  cent 


Hydrocarbons 12.30 

Sulphuric  acid 4 . 33 

Hydrochloric  acid 1 .33 

Ammonia 1 . 37 

Metallic  iron  and  black  magnetic  oxide 2 . 63 

Mineral  matter,  chiefly  silica  and  ferric  oxide.  .31 .24 

Organic  matter 1 . 20 

Loss  and  undetermined 6 . 60 


/      inert. 

^  Corrosive, 

j     7. 03  per  cent. 

Metallic. 

Mineral. 
)7.80  per  cent 
)  decomposable. 


100.00 


Corrosive  Elements  of  Smoke  and  Fog. 

The  composition  of  smoke  in  the  cities  of  London  and  Glasgow  as 
analyzed  by  Mr.  W.  R.  Button  *  also  includes  the  soot  deposited  by 
the  smoke  after  being  diluted  by  the  air  under  the  conditions  of  an 
English  foggy  day. 


Substance. 

London. 

Glasgow. 

Tar  and  oil  

10  000/  1  Non- 
«  W7     corrosive, 
53-18%J  71.18% 

14.40%] 

S:£|  i  MiT' 

i  new  I     an(l 
i'jKS     Metallic, 

U.dU%       1R   7907 

0.20%  |  18-72% 
2.08%  J 
4.60% 

*(??%?     Corrosive 
°'25%  ^  elements, 

U-  <U/0    |    in    -,f)(y 

1.75%  I  l°-10% 
2.80%j 

15.00% 
35.70% 

25.70% 

0.70% 
0.30% 
0.80% 
trace 

7^90%  : 
0.40% 
none 
trace        ' 
2.80% 
7.20%j 

Non- 
corrosive 
'  substances, 
50.70% 

Mineral 
and 
h  Metallic, 
27.80% 

Corrosive 
substances. 
21.50% 

Carbon  

Sand 

Iron 

Soda  

Lime 

Magnesia 

Potash  

Phosphates  of  lime  and  magnesia  . 
Sulphuric  acid  

Chlorine   .        ... 

Sulphocyanogen  
Carbonic  acid.  .  . 

Ammonia.  .  . 

Water  .  . 

100.00%     100.00% 

100.00%     100.00% 

Dr.  W.  G.  Blake  found  that  the  dust  and  soot  in  the  central  dis- 
trict of  Edinburgh  in  1902,  deposited  in  open  vessels,  amounted  to 
38  ounces  per  square  foot,  or  about  24  pounds  per  year  for  every 


* '*  Chemistry  of  Coal  Smoke."     A  paper  read  before  the  Chemical  Section. 
Glasgow  Philosophical  Society,  Glasgow,  Scotland. 


416 


PROPERTIES   OF  SATURATED  AIR. 


100  square  feet  of  surface.  It  was  highly  charged  with  sulphuric 
acid,  albuminous,  vegetable,  and  animal  substances  as  well  as  soot 
and  cinders.  -  . 


THE  WEIGHT  OF  AIR,  VAPOR  OF  WATER,  AND  MIXTURES  OF  AIR  AND  VAPOR  AT 
DIFFERENT  TEMPERATURES  UNDER  THE  ORDINARY  ATMOSPHERIC  PRESSURE 
OF  29.921  INCHES  IN  THE  BAROMETER.  (Tnos.  Box.) 


pg 

Hs 

.2  **> 

.S3 

*  c 
I1  . 

Weight  of  a  Cubic  Foot  of  the 
Mixture  of  Air  and  Vapor. 

11 

—  - 
^  o 

1 

03    -M 

J_,    CO    fl 

.2  if 

II 

1l| 

d 
£ 

1. 

.S 

bft 

H 

£j    '~ 

fc 

3  £jj 

jps<2 

"o^ 

*-•-§ 

>j 

*SJA 

>•$ 

b^ 

^|fa 

03  "trt*    » 

S°x 

|««<o 

«'! 

§£ 

<D 

Q1© 

1 

"SfleS 

•o-b  £ 

fe  gl 

0  £  J 

^^ 

•si 

fej 

O" 

•gsS 

£ 

§  "^ 

^J  2 

j^  fl 

1*1  §  g 

« 

"O 

rH 

g 

111 

111 

|s| 

•2~XhH 

|| 

1^ 

11 

*CJ  ^ 

If 

0 

.0  Q>3 

£ 

s^v 

ss's 

1 

*"* 

H 

1 

Degrees 

Lbs. 

32 

1.000 

.0807 

.181 

29.740 

.0802 

.000304 

.080504 

.00379 

263.81 

42 

1.020 

.0791 

.267 

29.654 

.0784 

.000440 

.078840 

.00561 

178.18 

52 

1.041 

.0776 

.388 

29.533 

.0766 

.000627 

.077227 

.00819 

122.17 

62 

1.061 

.0761 

.556 

29.365 

.0747 

.  000881 

.075581 

.01179 

84.79 

72 

1.082 

.0747 

.785 

29  .  136 

.0727 

.001221 

.073921 

.01680 

59.54 

82 

1.102 

.0733 

1.092 

28.829 

.0706 

.001667 

.072267 

.02361 

42.35 

92 

1.122 

.0720 

1.501 

28.420 

.0684 

.002250 

.070717 

.03289 

30.40 

102 

1.143 

.0707 

2.036 

27.885 

.0659 

.002997 

.068897 

.04547 

21.98 

112 

1.163 

.0694 

2.731 

27  .  190 

.0631 

.003946 

.067046 

.06253 

15.99 

122 

.184 

.0682 

3.621 

26.300 

.0599 

.005142 

.065042 

.08584 

11.65 

132 

.204 

.0671 

4.752 

25.169 

.0564 

.006639 

.063039 

.11771 

8.49 

142 

.224 

.0660 

6.165 

23.756 

.0524 

.008473 

.060873 

.16170 

6.18 

152 

.245 

.0649 

7.930 

21.991 

.0477 

.010716 

.058416 

.22465 

4.45 

182 

.306 

.0618 

15.960 

13.961 

.0288 

.020536 

.049336 

.71300 

1.402 

212 

1.367 

.0591 

29.921 

0.000 

.0000 

.036820 

.036820 

Infinite 

00.00 

OILS  AND  SOLVENTS. 


417 


VEHICLES  AND  SOLVENTS. 


Substance. 

Specific 
Gravity. 

Pounds  per 
Gallon. 

Bisulphide  of  carbon   CS2.  ...                            

1.26 
1.56 
0.730 
0.712 
0.9224 
0.9230 
0.9288 
0.9205 
0.9292 
0.9325 
0.9332 
0.9245 
0.9299 
0.9411 
0.8993 
0.9887 
0.9910 
0.960 
0.839 
0.811 
0.870 
0.855 
1.000 

0.91 
0.794 
0.816 
1.10 
1.849 
1.97 

1.2 

1.52 
1.524 
0.11636= 

1.261  to  1.27 
0.93 

10.513 

13.00 
6.09 
5.94 
7.696 
7.701 
7.749 
7.686 
7.741 
7.781 
7.786 
7.723 
7.759 
7.853 
7.50 
8.2497 
8.269 
8.01 
7.00 
6.77 
7.262 
7.134 
8.344 

7.59 
6.625 
6.808 
9.178 
15.43 
16.438 

10.020 

12.710 
12.716 
8.594  cu.  ft. 
per  pound. 

10.597 

7.76 

Tetrachloride  of  carbon,  CC14.  .    .                

Benzine   62°  B.  .  .                                       

"         66°  B  

Cotton-seed  oil,  crude.  .     .    .        

"           "     refined  yellow  

"    water-white  

Cod-oil  (tanners')  

Menhaden-oil,  dark  

"          light  

Porgy-oil.  .                        

Poppy-seed  oil.  ...         

Linseed-oil,  raw,  pure  

"          boiled    pure 

Lucol  (substitute  for  linseed-oil.)  

Resin-oil,  third  run  

"        other  runs  

u             «         « 

Petroleum,  Lima,  crude  

"           other  brands 

Turpentine-oil,  pure  (C10H16)  

commercial  

Water.  .  .                          

Other  oils  and  fats,  see  page  418. 
Ammonia   27.9  per  cent  .*.  .    .    . 

Alcohol,  pure.                  

"        95  per  cent  

Acetic  acid   hydrated  (C  H  O3) 

Sulphuric  acid  (H  OSO3) 

"             "     anhydrous  (H2SO4) 

Muriatic  acid     )  RC1       (R  Q  } 

(Hydrochloric)  f 
Nitric  acid  (HNO3) 

Carbonic  acid  CO2 

"             "    gas 

Glycerine,  (C3H8O3)  Carbon,       40  per  cent  "1 
Hydrogen,    9     "      "     }•  

Oxygen       51     "      "    J 
Olein 

418 


FATTY   ACIDS  AND  SOLVENTS. 


Substance. 

Specific 
Gravity. 

Remarks. 

Acrolein,              C3H4O.  . 

• 

Acrolic  acid,        C3H4O2.                  

Acetic  acid,         C2H4O3.  .             

1.0635 

Margaric  acid,     C^H^Og  

0.810 

Oleic  acid             C,8H3  O2 

0.808 

Oleic  ether           C20H3/)2 

0.807 

(Dissolves  all  solid  fats,  .stearic,  palmitic, 
and  other  fatty  acids.) 
Stearic  acid,        CjsH^O^.  .  .           

0.805 

Vegetable  fatty-oil 
acids. 

Palmitic  or  )       n  TT   n 
f)     .        .  ,    >•  .     \j,Rtiw\jn  

0.803 

Benic  acid    f 
Glycerine  ether  C3H12O,5 

Stearic  acid         C]8H3CO2.    .  . 

1  01 

Stearic  ether        C19H38O2 

1  0 

Stearine                C2,H49O4.  . 

0  9245 

Glycerine,            C3H8O3.     . 

1.268 

(Paraffin,            C27HM  or  C27Hr>6  
(  Carbon,       85.31  per  cent. 
~   (Hydrogen,  14.44     "      " 
Fibrine: 
Vegetable,  C-4  2H7  .N.,  

0.87 
1  2568 

Melts  at  112°  to  1  49°  F. 
Boils  at  700°  F. 

Fish,           Cl  H'N  'S115-. 

1  2617 

Albumin: 
Animal,      C53  4H7  XN15  7  

1.2351 

Vegetable,  C^  -,H7  ,N,,  , 

1  2412 

{Bisulphide  of  carbon,  CS2..  . 

1  072*        1 

i  Carbon,    15.8  per  cent  
""  }  Sulphur,  84.2     "      "  .  .  .  . 

2.6296  to 
2  6447  t 

Boiling-point  109.4°  to 
118.4°  F. 

Tetrachloride  of  carbon,  CC14. 

1  56           \ 

Boils  at  1  70°  F.;  weight 

Linoleic  acid,                     C16H2(O.,.  .  .    . 

1 

0  953 

13  pounds  per  gallon. 

Oxylinoleic  acid,               C,6H2BO5  

1.016 

*  At  32°  F. 


t  At  60°  F. 


Proportions  of  Oil  in  Pigment  Pastes. 

It  is  often  important  to  know  the  amount  of  oil  necessary  to 
form  a  paste  with  the  different  pigments.  This  amount  necessarily 
varies,  owing  to  the  condition  of  some  of  the  pigments  before  mixing 
and  the  fineness  of  grinding.  The  following  is  a  general  average  of 
the  percentage  of  oil  in  100  pounds  of  commercial  paste  from  pure 
pigments: 

White  lead,  pure 8  to    9  per  cent. 

Red  lead,  pure 12  "  " 

Sublimed  lead 10  "  " 

Zinc  oxide  or  white,  French 16  "  " 

"       "       "       "      American 18  " 

Whiting  paste 20  " 

"      putty 18  "  " 


PROPORTION   OF  OIL  IN  PIGMENT  PASTES.  419 

China  clay 23  per  cent. 

Terra  alba 22  "  " 

Barytes 8  to  10  " 

Silica,  or  silex,  floated 25  "  " 

Lampblack 65  to  70  "  " 

Drop-black 50  "  " 

Gas-black SO  to  84  "  " 

Mineral  black 35  to  40  " 

Graphite 30  to  35  "  " 

Mineral  brown 22  to  25  "  " 

Vandyke  brown 45  to  50  "  " 

Burnt  Sienna,  American 35  "  " 

Italian 50  " 

Raw   Sienna,  American 40  "  " 

Italian 55  "  " 

Burnt  umber,  Turkey.  . 42  to  45  "  " 

"           "      American 35  "  " 

Raw  umber,  Turkey 40  " 

"          "      American 35  "  " 

French  ochre 30  to  33  "  " 

Yellow      "       American 28  to  30  " 

Oxford      "      English 25  to  30  "  " 

Indian  red. 20  "  " 

Oxides  of  iron 23  to  25  "  " 

Venetian  red 23  to  25  "  " 

Tuscan  red 23  to  26  "  " 

Rose  pink 30  to  35  "  " 

Carmine,  French 50  to  54  "  " 

Vermilion,  American 20  to  22  "  " 

English 15  to  18  "  " 

"         artificial  (according  to  the  specific  gravity  of  the 

pigment) 15  to  30  "  " 

Chinese  or  Prussian  blue 50  "  " 

Ultramarine  blue 30  "  " 

Light  chrome  yellow 20  "  " 

Medium  chrome  yellow 26  "  " 

Dark  or  orange  yellow 22  "  " 

Chrome  green,  pure  (according  to  the  shade) 26  to  35  "  " 

Chrome  green,  commercial  (the  lightest  shades  require  the 

least  oil 15  to  23  "  " 

Yellow  lake,  French 38  " 


420 


ELECTRO-CHEMICAL  ELEMENTS. 


Berzelius'  series  of  electro-chemical  elements  and  their  symbols 
are  as  follows  (those  in  italics  are  the  pigment  class) : 


Element  . 

Symbol. 

Element. 

Symbol. 

Element. 

Symbol. 

Oxygen.  . 

Q 

Silicon.         .    .    . 

Si 

Manganese 

Mn 

Sulphur  
Silenium.  .  .  . 

s 

Se 

Hydrogen  
Gold  

H 
Au 

Uranium  
Cerium.  .  .      . 

U 
Ce 

Nitrogen.  .  .    . 

N 

Osmium  

Os 

Thorium  

Th 

Fluorine 

F 

Indium 

Ir 

Zirconium 

Zr 

Chlorine 

Cl 

Platinum.  .  .  . 

Pt 

A  luminium 

Al 

Bromine 

Br 

Rhodium  

R 

Didymium 

D 

Iodine  
Phosphorus  . 

I 
P 

Palladium  
Mercury 

Pd 
He 

Lanthanum  
Yttrium 

La 
Y 

Arsenic  

As 

Silver.  

Ag 

Glucinum  

G 

Vanadium 

V 

Copper 

Cu 

Magnesium.  . 

Mg 

Molybdenum.  . 

Mo 

Bismuth 

Bi 

Calcium 

Ca 

Tungsten.  . 

W 

Tin 

Sa 

Strontium. 

Sr 

Boron  

B 

Lead     . 

Pb 

Barium  

Ba 

Carbon  

c 

Cadmium  

Cd 

Lithium  

L 

A  ntimony 

Sb 

Cobalt 

Co 

Sodium 

Na 

Tellurium  
Tantatum.  . 

Te 
Ta 

Nickel  
Iron 

Ni 
Fe 

Potassium  

K 

Titanium.  ... 

Ti 

Zinc 

Zn 

Each  metal  is  electro -negative  to  all  that  follow  it  in  the  list, 
and  electro-positive  to  all  that  precede  it,  dihite  sulphuric  acid  being 
the  exciting  liquid.  Alloys  of  the  metals  vary  the  above  order  of 
location  to  a  small  extent,  and  all  excitant  acids  also  change  the 
order  slightly. 

The  amount  of  electro-chemical  force  developed  in  the  oxidation 
of  metallic  substances  and  their  oxides  is  given  on  pages  353,  354, 
355. 


UNIVERSITY 

or 


GENERAL  INDEX. 


ACIDS 


Acrolic,  229 

Benic,  220 

Carbonic,  62,  74 

Fatty,  220,  240,  418 

Linoleic,  linolenic,  219,  220,  226 

Margaric,  220 

Muriatic,  276,  277 


Nitric,  301 
Oleic,  200,  250 
Olein.  250 
Oxylinoleic,  219 
Palmitic,  220 
Pyrol  igneous,  100.  195 
Sulphuric,  276,  277 


ADULTERANTS. 


Aniline,  40 

Brick-dust,  52,  58,  187 
Cement   hydraulic,  149,  154,  171 
General,  148,  311,  312 
Graphite,  138,  139 
Iron  oxide,  37,  40 
Lampblack.  102 

Linseed,  linseed-oil,  215,  216,  221,  226, 
236,  240,  242,  248 


Mixed  paints,  96 

Red  lead,  48,  57,  58 

Resin-oil,  cotton-seed  oil,  241,  242 

Spirits  turpentine,  196-198,  200 

Tin,  terne-plate,  176,  183 

White  lead,  65,  77-80 

Zinc  oxide,  92,  94-96 


ANALYSES. 


Acrolic  acid,  acrolein,  229 
Air  and  smoke,  325,  326 
Asphalt,  asphaltum  paint,  103 
Barytes,  412,  413 
Bessemer  paint,  145 

slag,  147 
Bisulphide,    tetrachloride    of  carbon, 

203.  204,  409 

Cements,  hydraulic,  Portland,  149,  150 
Clays  (terra  alba),  kaolin,  190,  409 
Coal-gas,  coke-oven  gas-tar,  106-109 
Copperas,  40,  41 
Corroded  iron,  338 
Euphorbium,  255 
Glycerine,  408 
Graphite,  137 
Gypsum,  408,  412 
Inert  pigments,  189,  192,  408 


Iron  ores,  oxides,  29,  30,  412 

Lead  ores,  45,  46 

Linseed,  linseed-oil,  216,  217,  218 

Litharge,  59,  409,  412 

Lucol,  417 

Manganese  dioxide  (pyrolusite),    227, 

412 

Marl,  190 

Mixed  paints.  311-313 
Mulder's  brick-dust  paint,  52 
Ochre,  42 
Oil-cake,  217 
Oils,  siccative,  non-siccative,  217,  218, 

222,  223 
Olein,  250 

Orange  mineral,  60,  409 
Petroleum,  105 
Pitch,  107 

421 


422 


GENERAL  INDEX. 


Red  lead,  47,  408,  412 

Shellac,  114,  115 

Silicate  of  iron,  338 

Slags,    blast-furnace,    mineral    wool, 

tetrabasic    phosphate  of  lime,    146, 

147,  409 

Snow-water,  smoke,  415 
Sublimed  lead,  84,  408,  412 


Tubercles,  324,  329,  378 
Turpentine-oil,    dead-wood    oil,    193, 

195,  196 
Umber,  43 
Vermilion,  409,  412 
White  lead,  74,  75,  408,  412,  413 
Zinc  oxide,  89,  90,  93,  94,  409,  412 


INDEX. 


A. 


Abbe's  refractometer  tests  for  oils,  240 
Acheson's  electric  graphite,  141, 144, 421 
Acids,  adulterants,  analyses,  417 
Acrplic  acid,  acrolein,  2^9,  230,  253,  418 
Action  of  light  on  paint,  3-10 
Air  and  vapor  mixtures,  416 
"   refraction,  coloring  power,  3,  5,  187 
"  in  tunnels,  325-338 
Albumin  and  mucilage  in  oils,  218,  220, 

222,  238,  240 
Alloy    corrosion,    aluminum,    arsenic, 

copper,  276,  332,  343,  344,  401-408 
Anchorage  metal   corrosion,  316,  389, 

397 
Anchorage  metal  electrolysis,  387 


Animal  lampblacks,  102 

"      oils,  224,  245,  250,  251 
Aniline  in  iron  oxide  paint,  40 
Andrews'  corrosion  experiments,  331 
Angus  Smith's  anti-corrosive  coating, 

123-127 

Anti-corrosive  mortar,  269 
Antoxide  paint,  290,  297,  300 
Argentine  Republic,  linseed,  213,  214 
Asphaltum  and  asphalt,  103-109 

paints,  104,  105,  129,  205, 

284-292,  297 
Atmospheric  gases,  acid,  influences,  8 

14,  92,  93, 183,  228,  265,  266,  291-295, 

324,  325,  397,  406,  411-413 


B. 


Barytes,  blank  fixe,  6,  53,  77,  80,  95,  96 

140,  185,  186,  281,  282,  312,  313,  408- 

413 

Barytes-Beckton  whites,  66,  67,  95,  96 
Baked  Japan  coatings,  119-123,  298 
Benzine,  116,  216,  314,  319,  411,  417 
Berlin  blue,  bone  lampblacks,  99, 100 
Bessemer  paint,  145-148,  296.  300 
Bisulphide,    tetrachloride    of    carbon, 

203-207,  223,  417 
Blast-furnace,  Bessemer,  cement  slags, 

147,  150 
Blistering  and  crazing  of  paint,  25,  216, 

319.     See  Peeling 
Boiling-point  of  coal  tar,  124-127 

"  turpentine,  193 
Boiling  linseed-oil  processes,  225-239 


Boiled  linseed  coatings,  14-16,  23-25, 
281-283,  296,  389 

Brick  water-proofing,  efflorescence,  113, 
164, 165 

Brick-dust  paints,  48,  52,  53,  187,  188 

Bridge  anchorage  and  cable  corrosion, 
389-392,  397 

Bridge  anchorage  and  cable  electroly- 
sis, 387 

Bridge  anchorage  and  cable  painting, 
316 

Bridge  paints  and  coatings,  389-392 
tests,  279-303 

Brooklyn  gas-,    water-pipe  corrosion, 
392,  393 

Burning  off  mill-scaleand paint,  277, 278 

Bung-hole  oil.  209, 210, 233, 234, 238, 246 


C. 


Calcining  iron  ore.  30,  31,  33 
Candle-tar  pitch,  129-136 
Carbonic  acid  in  air,  325,  415 

"  "in  pigments,  62,  74,  411, 

413,  415,  417 

Carbonized  coating,  287,  291-294,  297 
Carbon    bisulphide,    tetrachloride    of 

carbon,  203-207,  223 


Carbonates  of  lead,  lime,  zinc,  7  45 

61,  64,  75 

Carbon  and  bone-black  paint,  281 
"       group  of  pigments,    98,    104- 

110 

litharge,  red-lead  mixtures,  281 
paints  and  varnishes,  110,  111, 
284-290 

423 


424 


INDEX. 


Carter's,  Clinchy's  quick  process  white 

leads,  66-69 
Cast  iron  not  exempt  from  electrolysis, 

393 
Catalysis,   catalytic    action   in   paint, 

225,  267 

Caustic  action  of  lime,  cement,  con- 
crete, 13,  150,  268-270 
Caustic  action  of  roasting  ore,  32-34, 

40 
Caustic    compound,  removing    paint, 

277,  278 

Cements,  Portland,  etc.,  149-166 
"         coatings,  152-163 
"  "         porosity,  155,  156 

"        neat,  strength,  154 
"         iron  sulphide  in,  151 
Cellular  formation  of  wood,  12 
Cerussite,  cerussa,  60 
Coal-tar,  analysis,  tension  in  boiling, 

124 
Coal-tar    coatings,    107-109,    124-136, 

338 

Coal-tar  paints,  286  to  291 
"        dipping-tank,  134 

distillation,  125-127 
Coal-    and    water-gas    tars,    101-109, 

123-135,  400 
Colophony,  193 
Concrete  qualities,  154-163 

"       voids  in,  produce  corrosion, 

158,  159 
Cortisine,  233 
Chemical    action   in    corrosion,    353- 

359,  362 
Chemical  action    in    paint,   8-55,   92, 

93 
Chemical  composition  of    glycerides, 

oils,  and  fats,  10,  78,  218,  237,  240, 

250,  417,  418 
Chemical  changes,  tests,  linseed  and 

other  oils.     See  Linseed  Oil. 
Chemical  action  of  soils,  161,  378,  379, 

393 
Chinese  wood-oil,    251-260  ;  lacquers, 

279 
Chinese-Japanese    natural    varnishes, 

256-260 

Chrome  blue,  green,  red,  yellow,  3 
Chalk,  carbonate  of  lime,  184,  282 
Chalking  of  white  lead,  74-76,  80,  316, 

391 
Chinese,  celestial,   ultramarine  blues, 

281,  282 

Cooper's  lines  in  corrosion.  357 
Copal  fossil  resins,  111-118,  199,  224, 

242,  303,  400,  401,  405,  407 
Copperas  and  oxides,  7,  36,  40,  266 
Copper,    metallic   salts   corrosion,  89, 

177,  264,  336,  344,  362,  379,  381,  395 


Cleaning  paints,  metal,  8,  12,  13,  20, 

270,  277,  278 
Clarifying    linseed-oil,  223,  234,  235, 

243-245 

Coloring,  covering  power,  2-5,  246 
Combustion  gases,  effects  on  paint,  8, 

9,  54,  175,  294,  301,  302 
Commercial    white    lead,   57,   58,   65, 

77-80 
Compound  paints,  3,  6,  7,  12,  30,  36, 

186,  281-283,  291,  296,  299,  311,  312- 

315,  319;  marine  use,  398,  399 
Compounds,   use    of    zinc  in   boilers, 

method   to   prevent    corrosion,  182, 

340,  343.  345-348 

Compounds,  Wurtz's   method   to  pre- 
vent corrosion,  183,  328,  329,  339 
Changes  in  cast  iron  from  fresh-  and 

sea-water  exposure,    323,   324,    329, 

330,  338,  360 
Changes  in  paints,  pigments,  55,  76,  92, 

95,  265-2(57,  411-413 
Coal,  cinder,  and  soil  corrosion,   120, 

161,  162,  378,  379,  332 
Concrete  corrosion,  154-158,  389,  395 
Corroding  effect  of  water  in  boilers, 

375 
Cost  of  water-pipe  coatings,  124,  125 

"     "   galvanizing,  177,  180 

"     "  painting,  19,  20;  by  spray,  304- 
o06 

"     "  sand-blasting,  273,  274 
Crocus,  26 

Crystalline  white  lead,  72,  77,  83 
Cubic  feet  and  weight  of  gases,  411 
Corrosion: 

Admiralty,  Board  of  Trade,  Lloyd's, 
Th wait's  rules,  324,  325,  331 

alloys,  aluminum,  arsenic,  etc.,  152, 
401,  402,  405-407 

anchors  and  chains,  334 

anti-corrosive  and  anti-fouling  paints, 
400-407 

boiler  sheets  and  rivets,  333,  334,  349 
"      metal  dissolved,  348 

bridge  cables  and  anchorages,    316, 
389-392,  397,  398 

cannon,  335 

car-wheels,    cold-rolled     iron,    327, 
328 

cast  iron,  wrought  iron,  steel,  rate, 
322,  323,  330-332 

cast-iron  cubes,  324,  325.  331 

central- station     heating-pipes,     347, 
348,  374,  375 

chill-irons,  328,  329 

cold  short,  hot  short,  and  laminated 
irons,  327,  332 

docks,  piles,  water-gates,  324-326 

Faraday's  law,  363,  388,  389,  392 


INDEX. 


425 


Corrosion: 
by  stress,  348-353 
floor  arid  sidewalk  beams,  161,  268- 

270,  274,  334 

French  torpedo-boats,  343,  346,  406 
from  electrolysis,  379-381 

"    sewage,  264,  328,  330 
gas-  and  water-pipes,  161,  261,  347 
Hambuchen's  rapid  method,  359-369 
hardened  and  burnt  steel,  361,  363- 

368 
how  induced,   26-28,  156,  157,  261, 

340,  343,  360-364 
how  prevented,  27, 134,  167,  170,  180, 

269,  270,  324,  328,  329,  339,    345, 

346,  379,  389,  391,  396 
-of  metals  in  contact,  262,  264,  340- 

342 
of  metals  in  oils,  414 


Corrosion: 
mine  pipes,  339 
New  York  Elevated   Railway,  261, 

295-297 
Peoria   water  stand-pipe,    152,  153, 

374-378 
steel  grillage,  anchorage  metal,  154, 

158-160 

stray  electric  currents,  386-389 
St.  Lawrence  River  Bridge,  298,  342 

363 

Tay  Bridge,  343 
rag  bolts,  392 

tee-rails,  cross-ties,  336-338,  386 
tin  roofs,  38,  39,  43,  44,  55,  183 
tunnel-shields,  metal,  157,  158,  324, 

327,  335,  389 
United  States  Navy  Yard  practice, 

263,  264 


D. 


Dangerous  paints,  8,  110,  120,  154, 
203,  204,  306 

Dangers  from  electrolysis  in  suspen- 
sion bridges,  396,  397 

Darkening  of  paint,  10,  40;  white  lead, 
77,  78 

Davis's  silicate  coating,  328,  339,  396 

Dead  oil  in  pipe  coatings,  127,  128 

Dead-wood  turpentine,  191 

Decay  of  paint,  8,  9,  13.  33,  35,  92,  93, 
120,  121,  162,  261-270,  318 

Decomposition  of  iron  in  corrosion, 
156,  157 

Delhi  column,  170,  171.  (Bower- 
Barff.) 

Designing  paint,  6,  16,  317,  318 

Dish  test  for  paint,  283-285 


Distillation  of  coal-tar  oils,  124, 126, 127 

Distillation  of  turpentine,  127-134 

Drying  of  linseed-oil,  131,  139,  218, 
220,  223,  235,  236,  238;  under  glass, 
237 

Drying  of  sulphuric-acid  oils,  7,  230, 
231 

Driers,  drying  of  paints,  7,  10,  43,  51, 
139,  140 

Dr.  Angus  Smith's  anti-corrosive  coat- 
ing, 124-127,  287,  394 

Dr.  Dudley's  boiled-oil  coating,  14 

"        paint  formula,  42 
"    Wurtz'santi- corrosive  process,  180, 
339 

Durable  metal  coatings,  287,  297,  300, 


E. 


Effect  of  driers,  dead  oil,  95,  114,  229, 

235,  303 
Effect  of  heat  on  boiling,  drying  oil  and 

paints,  8,  116,  227,  236,  237,  239,  246, 

247,  302,  303,  308 
Effect  of  heat  and  hydric- sulphide  on 

paint,  54,  77,  80,  94,  116,  140,  186, 

287-291,  298,  302,  303 
Effect  of  sea-air,  sea- water,  264,  287- 

294,  324,  334,  335,  340-344,  400-407 
Effect  of  sewage,  condensation  water, 

264,  330 
Effect  of  strain  in  corrosion,  349-352 

"       "  spray  painting,  frost,  11,  246, 

308 

Efflorescence  on  brick  walls,  163,  164 
Eiffel,  M.,  rag-bolt,  392 
Electrolytic  action  in  paint,  81,  35,  36, 

120,  149,  155,  318,  362 


Electrolytic  paints,  146,  373 

white  lead,  10,  71-73 

Electrolysis,  371-399;  action,  363;  de- 
fined, 370 

Electrolysis  in  buildings,  371;  bridges, 
cables,  373,  387-393 

Electrolysis,    coatings,    373,    389-391, 
396,  399 

Electrolysis  in  concrete  conduits,  395 

Faraday's   law,   363,  392; 
rate  of,  393 

Electrolysis  in  gas-pipes.  384;    water- 
pipes,  379,  383,  396 

Electrolysis,    Hambuchen's    rapid   ac- 
tion, 359-369 

Electrolysis  in  street  tee-rails,  386-388 
"          in  telephone    cables,    381, 
385,  388 

Electrolysis,  resistance  of  pipe  joints,  396 


426 


INDEX. 


Electrolysis,    Washington  Naval  Ob- 
servatory, 373 
Electro-chemical  action  for  preventing 

corrosion,  180-1  82,  328,  339,  340,  343 
Eleetro-chemical  action  of  metals  in 

contact,  260,  264,  340-342 
Electro-chemical  alloys,  401-407 

elements,  131 
"  "  "          Berzelius', 

420 
Electric  currents,  divided,  stray,  380, 

386,  399 
Electric  currents,  jump  and  shunt  of, 

372,  388 
Electric  voltages  in  corrosion,  372,  377, 

379,  380,  386-388,  394,  396 


Electric-furnace  graphite,  142-144 
Electro  -  zincing    processes,    solutions, 

174,  176,  179,  180 
Electro-motive  force  in  zinc  batteries, 

355 

Electro-motive  force  in  corrosion,  354 
"  '*•:**'  metal       under 

strain,  352,  353 

Enamel  paints,  116,  121,  130,  318-321 
Engineers'     indifference     to     cleaning 

metal,  20-26,  275,  276 
Euphorbium,    anti-corrosive   coatings, 

254-256,  391 
Essential  elements  in  a  good  paint,  1, 

20-22,  117 


F. 


Fading  of  paint,  10,  40  < 

Failure  of  cement  coatings,  152,  154 

157,  389,  390,  392,  396 
Failure  of  paint  coatings,  12,  20,  54-5  . 

297,  310-312.  316 

Failure  of  water-pipe  coatings,  132 
Fatty  turpentine,  199 

"    acids,  oils,   solvents,  10,  78,  218, 

220,  237,  238,  240,  250,  417,  418 
Feldspar,  188 ;  refractive  power.  3 
Ferredor  paint  (English),  290,  314;  see 

also  Crosley's,  Armor-scale,  Landers 

and  Torbay's,    314,  315 
Ferric-paint  test,  279-303 
Fibrin,  animal  and  vegetable,  418 
Flake     graphite,     19,    136-138;      see 

Graphite 
Floor- beam  corrosion,  277,  278 


Flax  plant,  linseed,  analysis,  etc.,  211- 

221 
Formulae  for  caustic  compounds,  277, 

278 
Formulae  for  enamels,  319,  320 

"    non-corrosive  cement,  268 
"    paints,  42,  295,  396 
"         "    Japan  driers,  208-210 
Fossil-resins,  111-118,  199,  224,  242,  303 

synthetical,  118 

"  varnishes,   marine   paint, 

318-320,  321,  400-407 
French  white  lead,  zinc  oxide,  66,  91 

ochre,  42,  312 
Fugitive  colors,  6,  265,  266 
Fulton's  flake  whites,  66-69 
Furnace  slags,  slag  cement,  mineral- 
wood  slag,  146,  147,  151 


G. 


Galvanizing,  hot   and  cold  processes, 
172-174,  180 

Galvanized  iron  paints  peel,  11, 174,  204 
"    cost,    177;     corrosion, 
174,  175.  178 

Galvanized  iron,  durability,    175,   181- 
183 

Galvanized  iron,  porosity,  173  ;  protec- 
tion, 175,  176 

Galvanized  iron,  hardness,     thickness, 
176,  178,  179 

Galvanized  iron  wires,  loss  of  strength, 
178-180 

Galvanized  iron,  painting   with    bisul- 
phide of  carbon,  207 

Galvanic  action  in  cements,  154 

"  "       "   different   metals  in 

contact,  330,  340,  341,  344 


Galvanic  action  in  metal,  oxide,  pig- 
ments, 186,  245,  363 

Gasolene  torch,  burning  off  paint  with, 
277,  278 

Gas-tank,  coal-tar  coating,  133,  165 

Gas  coal-tar  water-pipe  coatings,  287- 
291,  396 

Gas    and    water-pipe  corrosion,  elec- 
trolysis, 175,  376-386,  392,  393 

Gas-holder,  spray-painting,  304 

Gilsonite,  105 

Glass,  refractive  power,  3 
"      drying  oil  under,  239 

Glycerine,  glycerine  ether,  36,  218,  220. 
237,  238,^250,  417,  418 

Graphite,  analysis,  137  ;  importation.  17 

Gypsum,  6,  40.  188,  192,  269,  408,  413 

Graphite,  Acheson's  electric,  142-144 


INDEX. 


427 


Graphite  paint,  19,  52,    136-144,  281, 

285,  291-294,  297,  406.  408 
Graphite  paint  tests,  140-142 
Graphite,  electro -negative  character, 

146 


Graphitic     iron     in    corrosion,     329, 

338 
Graphite,  slow  driers,  297;  varieties,  136 


H. 


Hambuchen's  rapid  corrosion,  359-369 
Heat  influence  on  paint,  116,  227,  236, 

237,  239,  246,  247,  302,  303,  308 
Hematite  ores  and  pigments,  30-35 
Hydrate  of  lead,  hydrated  carbonates, 

4,  5,  46,  61,  66,  71.  74,  75 
Hydraulic  cement,  analysis  of,  149,  150 
"         coating,    water-pipes,    153, 

396 
Hydraulic  cracking,  setting,  strength, 

150-154 
Hydraulic  Portland  and  slag  cements, 

150,  151,  157,  290 
Hydraulic  protecting  metal,  153,  154, 

157-160,  164,  165,  395 
Hydraulic  cement  porosity,  155-157,396 


Hydraulic  cement,  effect  of  sulphur, 
iron  sulphide  in,  156,  157,  164,  171 

Hydraulie  cement,  Norton's  experi- 
ments, 158,  159 

Hydraulic  cement,  marine  coatings,  152 
rendering,  153,  162- 
165 

Hydraulic  cement,  waterproofing,  162 
"  "  use  for  steel  grill- 

age, 153,  154,  158-160 

Hydraulic  cement,  use  in  tunnels,  159, 
160 

Hydric-sulphide  effect  on  paint,  54,  80, 
140,  186,  287-291 

Hydrogen  evolved  in  corrosion,  28,  89, 
1  261,  354 


I. 


Immersion  test  for  paints,  279-284 
Inert  pigments,  35,  184-192,  286,  408, 

409 

Indian  red,  Venetian  red,  35,  37,  40,  41 
Influences  that   affect    paints,    20-26, 

275,  276,  300-308,  411,  417,  418 
Insulating  paints,  146,  373 
Inspectors  and  engineers,  cleaning  of 

metal,  20-26.  275   276 
Iodine  and  saponification  numbers  for 

oils,  243 
Iron  column  at  Delhi,  170,  171 


Iron,  changes  by  corrosion,  28,  324,  326, 
329,  330,  334,  3b7,  338,  342,  392 

Iron,  ores,  oxides,  analyses,  qualities, 
26-40 

Iron-oxide  pigments,  condensed  moist- 
ure gases,  35 

Iron-oxide  pigments,  durability,  6,  38 
"  "         mixing  defects,  37 

Iron  porosity  in  bars,  ingots,  tyres,  334 
"  oxide  pigments.  30-38,  138,  2»1, 
282,  284,  291-293,  313-315,  406,  409, 
410,  412,  419 


Japan  driers,  formulae,  201-208 

bung-hole  driers,  209,210, 
234.  238,  246 
Japan  driers,  baked  coatings,  119-122 


Japanese    and    Chinese   natural    var- 
nishes, 256-260 
Japanese  and  Chinese  lacquers,  279 


K. 


Kaolin  (terra  alba),  190 

Kauri,   fossil-resin  coatings,  112,   113, 

401-404 
Kerosene,  mineral  oils,  105 


Labor  cost  in  paint,  19,  21,  22 
Lacquers,  113,  256-260,  279 
Lampblacks   5,  16,  18,  49,  50,  98-102 
acids  in,  98,  100 


Knudson,  A.  A.,  electrolysis  of  street 

tee- rails,  386,  387 
Kirkwood,  James  R,  coating  cast-iron 

water-pipes,  123 


L. 


Lampblacks,  bleaching,  102;  combus- 
tion by,  101;  durability,  102,  155,  161 

Lampblack  mixtures,  49,  50,  281,  408, 
419 


r\ 


428 


INDEX. 


Lampblacks,  slow  driers,  50,  100,  102 
Lead   ores,    analysis,    45,  46  ;  amount 

corroded,  69 
Lead  carbonate,  chlorate,  45,  47,  60, 

61   66,  67,  74,  75,  232 
Lead,  hydrate  and  protoxide,  4G,  60,  66, 
,    71,  74,  75 
Lead  pigments,  48,  74,  75,  408,  412 

adulterants,  57,  58,  65, 

77-80 
Lead,  electrolytic  white,  70,  72,  73 

"      "Old    Dutch    Process"    white, 

61-75 
Lead,  pulp  white,  63 

"      sublimed  white,  83-88 

"      soap,  10,  49,  74,  75,  78,  86,  235, 

237,  238r  264,  266 
Lead   sulphide  and  sulphate,  36,  46, 

66,  94,  95 

Light  refracting  of  pigments,  3,  4,  5 
Linoleic,  linolenic,  and  isolinoleic  acids, 

219,  220,  226,  237,  418 
Linoleate  of  lead,  234.  239 
Linoleum,  94,  230,  233 
Linseed,  analysis  of,  216,  217  ;  seed  and 

sources  of  supply,  211,  213,  215 


Linseed  extraction  processes.  220  ;  in- 
spection, 219  ;  yield  of  oil,  218 

Linseed  fatty  acids,  220 

in  paint  pastes,  418,  419 
tests,  240-247  ;    transparency, 
54 

Linseed,    unripe  seed,    222,  223,    235, 
239,  242,  314 

Linseed,  sulphur  effects  on,  223 

Linseed-oil,  18;  analysis,  220 

adulterations,  219, 240, 242, 
248,  314 

Linseed- oil,  boiling  data,  127-129,  220- 
246 

Linseed-oil,  bung-hole  boiled,  209,  210, 
233,  234,  246 

Linseed-oil,  coloring  power,  3 
driers,  225-235 
drying,  131,  139,  218-223, 
235-239 

Litharge     analysis,     59  ;    driers    and 
qualities.   17,  47-49,   226.    232,  408 

Lithogen  silicate  paint  test,  291-293 

Lithopone,  94,  95   186.  283,  409 

Lucol,  249-251,  297,  417 


M. 


Maize,  grain  oils,  79,  223 

Manganese  driers,  41,  43,  206,  226,  227, 

232,  234,  238 
Manganese     dioxide,      analysis,     227; 

paint,  281 

Maltha  paints,  failure.  110,  297 
Marine  alloys  and  paints.  96,  400-407 
Marl  analysis,  190 
Mastic  resin  varnishes,  117,  391 
Masonry  waterproofing,  164   165 
Menhaden,   fish,    and    marine   animal 

oils,  224,  242,  243,  251 
Metallic  salt   corrosion,   89,  152,   177. 

236  263,  264,  336,  343,  344,  362,  379, 

381,  395 


Metallic  salt  base  of  pigments,  410,  420 
Merrimac  River  pollution,  328 

"    Chain  Bridge  paint,  102 
Mineral  wool,  147 
wax,  109 
"       rubber  paint,  289,  297 

pipe  dips,  129,  130 
Mineral-oil   effects     tests  for,  47,  57, 

241,  245,  303,  314 
Mineral-pitch  oils,  104 
Mill-scale  corrosion,  24,  154,  264,  271- 

278,  296,  361 

Mixed  paints,  93,  310-321 
Muriatic-acid  pickling,  224 
Mulder's  brick-dust  paints,  52,  53, 183 


N. 


Natural  varnishes,  256-260 

New  York  elevated  railway  paint  and 
corrosion,  262,  295-298 

Niagara  Falls  suspension  bridge  cor- 
rosion, 160,  389 


Nickel-coating,    177;   alloy  corrosion, 

406 
Non-corrosive  mortar,  269,  270 

"  water-pipe  enamel,  239 


O. 


Objection  to  water-tests  of  paints,  279 
Oil  and  corrosion  of  metals,  414 
"  fatty  acids,  and  solvents,  220-224, 
417,  4i8 
Oil  in  paint  pastes,  418,  419 


Oil  coatings,  14,  15,  24,  281-283 
at  the  mill,  23-25 
"          "        skin     experiments, 

244,  300-303 
"          "        sulphur  in,  245 


INDEX. 


429 


Oleic  acid  and  ether,  220,  418 

Olein  paint  oil,  250,  251,  417 

Oxides  of  lead  and  zinc,  6,  17,  46,  74, 

89-97,  175 
Oxides  of  iron,  6,  7,  10,  17,  26,  28,  30- 

37,  138,  157,  160,  281-284,  291-294, 

313-315,  334,  406,  409 


Oxidizing  of  paint,  7,  10 
Oxychloride  of  lead,  67 
Oxygen  in  pigments,  411,  412 
Orange    mineral,    17,    59;    Paris   red, 

60 
Organic  matter  in  paints,  10 


P. 


Paints,  adulterations,  analyses,  7,  40, 

421 
Paints,  atmospheric  gases,  acids,  light, 

action  on,  3-10.     See  A,  B,  Index 
Paints,  characteristics,  410 

changes  in,  8,    10,  55,  92,  93, 

265-268,  412,  413 
Paints,  coal-tar,  287-291 

coloring  and   covering  power, 

2-5,  186,  187 
Paints,  dangerous,    8,    110,    120,    154, 

203,  204,  306 

Paints,  destruction  of,  8,  9,  13,  264 
.     "       decay  of,  116.     See  D,  Index 
"       effect  of  heat,  frost,  sea-air,  sea 

water,    strain,    spray-painting,    etc. 

See  E,  Index 
Paints,  failures,  fading,  fugitive  colors, 

fossil  resins,  rain,  wind,  9,  14,  40 
Paints,  formulae,  42,  295,  396 

"       graphite,  galvanizing.     See  G, 

Index 

Paints,  hydraulic  cement.     See  H,  In- 
dex 

Paints,  inert  pigments.     See  I,  Index 
labor  cost,  19,  21,  22,  124,  135, 

313,  314 
Paints,  mixed,  93,  310-321 

Mulder's  brick-dust,  52.  53, 183 
"       Maltha  failures,  110,  297 
"       mineral-oil  effects,  tests  for,  47, 

59,  77,  241,  245,  303,  314 
Paints,  mixtures,  3,  7,  18,  49,  52,  54,  55, 

80,  93,  95.  96,  187,  188,  206,  319 
Paints,  peeling,  crazing,   livering,  11- 

14,  25,  44,  88,  92,  152,  174, 175,  216, 

227,  246,  308,  319 

Paints,  removal,  burning,  caustic  com- 
pounds, 277,  278 
Paints,  statistics,  7,  17,  314 


Paints,  thickness   of  coating,    19,    35, 

373 
Paint-tests,  16,  50,  55,  57,  58,  77,  81- 

83,  96,  279-303 
Paint -tests,  United  States  Navy  Yard, 

55,  96.     See  T,  Index 
Paint-tests,  marine,  400-407 

"      by  water,    279-281,  284 
Painting  by  contractors,  311,  318 

at  the  mill,  23-25 
"        with  boiled   oil,    14,  15,  24, 

281-283 
Painting  cement  coatings,  brick  walls, 

164,  165 

Painting  galvanized  iron,  11,  174,  175 
"        old  sign  boards,  102 

by  spray,  37,  304-309,  316 
Paraffin,  109,  418 

Pickling,  cleaning  metal,  25,  275,  276 
Pigments,  inert,  35,  184-192,  408,  409 
Pipe-dips,  129-135;  dipping-tank,  134, 

135 

Pitch,  candle-tar,  129-136 
Pitting    in  boilers  and   water  stand- 
pipes,  263,  333,  346,  360 
Polarization  of  turpentine,  194 
Poppy-seed  and  porgy  oils,  80,  222-224, 

240,  417 
Porosity  of  iron  and  steel,  173,  332, 

334 
Porosity  of  cement,    concrete,   paint, 

155,  156,  173,  176,  396 
Portland  cement,  150-158 
Printers'  varnish,  227 
Proportion  of  oil  in  paint  pastes,  3,  7, 

15,  37,  52,  54,  58,  418,  419 
Putty,  185,  186,  238 
Pyrolusite  analysis,  227;  paint,  281 
Pyroligneous  acid,  195-197 


Q. 

Quick-process  white  lead  or  whites,  65-79 


R. 


Railway-car   cleaning,   painting,   277, 

278,  306 
Rape-seed,  Russian  seed  oils,  215,  216, 

225,  245 


Red  lead,  19.  22,  46,  56,  60;  adultera- 

tions,  48,  57,  58 

Red-lead   changes,   54,   58,    183, 
412 


430 


INDEX. 


Red-lead  driers,  drying,  61.  52,  232 
"       failures    of,    coating,    54-50, 

297 

Red-lead  mixtures,  54,  58,  281;  lamp- 
black,   zinc  oxide,  49-56,  286,  299, 

312,  316 
Red  lead,  Mulder's  brick-dust,  53 

"     proportion  in  paint,  58,  419 

"       "    ready-mixed,  standard, 55,  57 
Red-lead  setting,  48,  49,  56,  57,  102, 

312 
Red-lead  tests,  57,  281,  283,  291,  299, 

300.     See  T,  Index 
Red  lead,  Paris  red,  orange  mineral, 

60 


Refraction  of  light  in  pigments,  3-6, 

10 

Ri'fractometer,  Abbe's,  240 
Resin,  resin-oils,    199,    224,   242,    303, 

319,  320 

Roasting  ores,  pigments,  32-34,  40 
Roofing  pitch  and  paint,  107,  129,  289, 

290 

Ruberine  paints,  pipe-dips.  130,  297 
Rust  produces  rust,  28,  157,  261,  392 

"  .  mill-scale  corrosion,  removal,  24, 

154,  264,  271-278,  296,  361 
Rust,  removal   by  burning,  pickling, 

steaming,  275-278 
Rust,  pipe-joints  burst,  2bl 


8. 


Sand-blast  apparatus,  271,  272 

cleaning,  8, 13,  22,  270-278, 

296,  308,  316;  costs,  273-276 
Sea- air,  sea- water  corrosion,    58.     See 

E,  Index 
Sea-air,  galvanizing,   324-326;   marine 

paints,  400-407 
Sewage,  condensation  water  in  boiler 

corrosion,  264,  328,  330,  348 
Setting  of  red  lead,  48,  49,  50,  102 
Shellac,  114,  115,  209 
Silica  floated,  blanc  fixe.  See  Barytes, 

Index 
Silica  graphite  paints,  138-140 

"      sand,  3,  191,  192 
Silicate  coatings  prevent  corrosion,  328, 

339 

Slags,  slag  sand,  slag  cements,  150 
Slag  paint,  290;  blast-furnace  slag,  147 
Snow-water,  smoke,  corrosive  elements 

in,  415 
Soaps,  lead  and  zinc,  10,  49,  74,  75,  78, 

86,  235,  237,  238,  264,  266 
Soapstone,  139,  191,  192 
Solvents,  oils,  and  fatty  acids,  117,  417, 

418 

Spanish-brown,  43.  44 
Specific  gravities,  3,  37,  49,  59,  83,  113, 

139,  143,  188,  190,  191,  193,  203,  206, 

218,  220,  221,  224,  237,  250,  253,  324, 

326,  408-411,  416-418 
Spennrath's  experiments,  300-303 
Spirits  of  turpentine,  116,  122.  193-202 
Spray-painting,  cost,  danger,  durabil- 
ity, effect  of  cold,  porosity,  37,  304- 

309,  316 


Stand-pipe  corrosion,  152,  153,  374-378 
Storage  of  linseed-oil,  255 
Stray  electrical  currents,  386-388,  397 
Steam,  removing  and  testing  paint,  277 
Steel,  effects  of  pickling,  275-277 
Strain  in  metal  corrosion,  9,  348-353 
Sublimed  lead,  83-87,  317,  412 
Suspension-bridge  cable  corrosion,  160 
electrolysis,  387, 396, 

397 
Suspension-bridge  failures,  390,  391 

'*  paint  coatings,  389, 

380,  391 

Substitutes  for  linseed -oil,  248-260 
Sulphur  compounds,  36,  37,  202 

•'  "  in    cement,    con- 

crete, 157 
Sulphur   compounds  in  cinders,    161, 

162,  269,  334 

Sulphur  compounds  in  oils,  245 
Sulphuric-acid  oils,  2,  23,  230,  231,  244, 

245 
Sulphuric  acid  in  cement,  concrete,  151, 

156.  157,  164,  171 
Sulphuric  acid  in  cinders,  161, 162,  269, 

334 
Sulphuric  acid  in  locomotive  exhaust, 

gases,  tunnels.  336,  337 
Sulphuric-acid  effects  on  oils  and  paints, 

7,  31.  33,  50,  58,  77,  113,  206,  244,  264, 

265,  266 
Sulphuretted  hydrogen,  9,  62,  140, 148, 

186,  329 
Sulphate  and  sulphide  of  lead,  iron, 

zinc,  45,  62,  66,  94,  95,  276, 409,412,413 
Sulphate  of  lime,  3,  36,  52, 154,  186,  189 


T. 


Talc,  soapstone  refraction.  3 
Tables  and  data,  408-421 


Tay  Bridge  disaster,  342 
Terra  alba,  190 


INDEX. 


431 


Tee-rail,  cross-tie  corrosion,  336-338, 
386 

Temperature  and  hydric  sulphide  ef- 
fects on  paint,  54,  77,  80,  94,  140, 
186,  287-291,  298,  302,  303 

Terne  ,  tin-plate,  and  tin-roof  corrosion, 
23,  38,  39,  42,  44,  55,  175,  176,  183 

Tetrachloride  of  carbon,  drier,  solv- 
ent, 206,  207,  417 

Tests  for  linseed-  and  resin-oils,  142, 
144,  199,  224,  240-247,  319,  320 

Test  for  paints,  10,  16,  280-286,  291, 
294,  301,  302 

Tests  for  white  lead,  77,  81-83 
"      "    red  lead,  55-58,  299,  300 
"      "    zinc  oxide,  96 
"--.    "     turpentine,  196-198 


Thermo-electro   and   chemical  actions 

in  paints,  31,  35,  36,  120,  149,  155, 

318,  362 
Thickness   and  porosity  of  paint,   19, 

35,  373 
Tile  and  brick-dust  paint,  48,  12,  53, 

187,  188 

Toch's  water-proof  paint,  1 63,  165 
Torpedo-bcat  corrosion,  343,  346,  406 
Tunnel     metal-shield    corrosion,    157, 

158,  324,  327,  335,  389 
Turpentine,      analysis,      adulteration, 

qualities,  51,  193-201 
Turpentine,   dead-wood,  195 

Douglas  fir,  199,  202 
fatty,  199 


U. 


United   States  Astronomical  Observa- 
.  tory,  eif  ect  of  stray  electrical  currents, 

373 
United  States  Navy  Yard  paint  tests, 

96,  286,  400-407 


United   States   steamship,  electrolysis 

in,  398,  399 
Umber,  43 
Ure,  Dr.,  analysis  of  linseed-oil,  216, 

217 


Vapors,  atmospheric,  weight,  411,  416 
"  "  acids  and  gases, 

influence  of.     See  A,  Index 
Varnishes,  qualities,  111-113,  402,  407 

commercial  brands,  116 
"          natural,  non-corrosive,  256- 
260 
Vegetable  oils,  number  of,  221-223 


Ventilation  in  ships,  162  ;  tunnels,  337 
Vermilion,  vermilionette,  3,  60 
Viaduct  corrosion,  painting,  262,  263, 

296-300 
Voltages  in  corrosion,    372,  377,  379, 

380,  386-388,  394,  396 
Volume,  weight,  specific  gravities,  408- 

420.     See  S,  Index 


W. 


Wandering  electricity,  386-389 
Water  and  air  mixtures  416 

"      corrosibility  in  boilers,  375 

"      corrosive  elements  in  snow  and 

smoke,  415 
Water,  effects  on  paint,  5,  8,   14.    See 

E,  Index 
Water-gas  and  coal-gas  tars,  105-109, 

123-135,  400.     See  0,  Index 
Water-  and  gas-pipe  coatings,  128-136, 

161,  261,  266,  347,  379,  380,  381 
Water  and  gas-pipe  corrosion,  132, 161, 

261,  347 
Water-  and  gas-pipe  electrolysis,  379, 

383-385,  392,  393,  396 
Water-  and  gas-pipe  testing,  123,  124, 

132,  133 
Water  in  linseed-oil,  58,  128,  218,  222, 

245-247,  285,  318 


Water  tests  for    paint,  279-281,  284 
Water-proofing  and  paint,  15,  163-16o 
Weight,  list  and  volume  of  gases,  fats, 

fatty  acids,  and  solvents,    220-'224, 

417,  418 
Whiting,   covering  power,  refraction, 

3,  185 

White-lead  ores,  45,  46;  analysis,  74,  75 
adulterants,  57,  58,  65,  77- 

80 
White-lead  carbonate,  hydrate,  64,  66, 

70,  71 
White  lead,  "  Old  Dutch  Process, "61- 

66,  69,  76,  83 

White  lead,  electrolytic,    70-73;    sub- 
limed, 83-88,  317 
White-lead  tests,  77,  81-83 

qualities  of  a  good,  74-78 
in  marine  paint,  96,  289 


432 


INDEX. 


White  lead,  zinc    oxide,    and    barytes  I  Wooden-structure  paints,  6-8,  34,  36, 
mixtures,  7,  77,  80,  93,  96,  312,  316  80,  81,  96,  246 


Y. 


Yellow  pine,  area  available  for  turpen- 
tine, 198 
Yellow  pine  distillation,  195 


Yellow  pine,  painting,  80,  81,  96,  246 

"      paint  size,  80,  81 
Yellowing  of  oil  and  white  lead,  7, 10, 40 


Z. 


Zanzibar,  fossil  resins,  111-118 

Zinc,  metallic,  89;  consumption,  91 
"     ores,  calamite,  89;  zincite,  91 
"     alloy  in  galvanizing,  177 
"     carbonate,  89;  sulphide  and  sul- 
phate, 77,  92,  9^,  95,  96,  409,  412 

Zinc,  electro-chemical  and  galvanic 
action  in,  98,  174-183;  E.  M.  F.  in 
batteries,  353,  355 

Zinc,  galvanizing,  172-183 
' '     oxide,  history,  91 ;  French  brands, 
91,  92 

Zinc-oxide  adulterants.  92-96 

changes  in,   77,  79,  80,  93, 
413 

Zinc-oxide  pigments,  77,  78,  80-97 


Zinc-oxide  marine  paints,  96,  286,  405- 

407 
Zinc  oxide  and  white  lead,  53,  80,  81, 

92-96,  312,  316 

Zinc-oxide  tests,  96,  97,  405,  407     - 
Zinc,  use  in  steam-boilers,  128,  339-346 

"      "     to  prevent  corrosion,  173-181, 

344-348 
Zinc-salt  paint  driers.  232 

"    sheets  and  roofing  durability,  23, 

181-183 
Zinc  soaps.     See  L  and  S,  Index 

"    whites  and  lithopone,  94,  95,  186, 

2r>2.  409 
Zincing  solutions,  176 


ADVERTISEMENTS. 


INDEX    TO    ADVERTISEMENTS. 


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ground  in  paste  form  and  kept  indefinitely 
without  hardening.  Pound  for  pound  it  will 
cover  20%  more  surface  than  any  other  lead 
pigment,  and  with  boiled  linseed  oil  it  makes  an 
indestructible  paint  for  iron  and  steel  surfaces. 
It  can  be  obtained  from  the  manufacturers  direct  or 
from  any  reputable  paint  grinder — in  dry,  paste 
or  liquid  form. 


A   BOOKLET  OP   DETAILED   INFORMATION  FOR    THE  ASKING 


RICHER    LEAD   COMPANY 

EASTERN  SALES  OFFICE:  WESTERN  SALES  OFFICE: 

100    WILLIAM     STREET  TACOMA    BUILDING 

NEW   YORK  CHICAGO 

WORKS:  JOPLIN,  MO, 

6 


flCflESON  GRflPHITE 


Fellow  Readers : 

We  have  but  one  suggestion  to  add  to  the  pages  of  this 
book — Determine  a  Standard  for  Graphite  Paints.  There  is 
to-day  absolutely  no  standard.  The  so-called  graphite  pigments 
contain  anywhere  from  20%  to  80%  of  impurities  and  adulter- 
ants of  a  heterogeneous  character.  Sometimes  they  contain  no 
graphite.  In  consequence  many  engineers  are  imposed  upon, 
and  there  are  many  failures  of  such  protective  coatings. 

We  are  naturally  interested  in  this  matter,  as  Acheson 
Graphite  Paint  Pigment  fully  meets  all  the  conditions  which  have 
ever  been  found  of  value  in  graphite  pigments.  It  is  manufactured 
in  the  Electric  Furnace  and  contains  all  the  merit,  with  none  of 
the  disadvantages,  of  the  natural  graphites.  We  guarantee  the 
Purity,  Uniformity,  and  Inert  Quality  of  Acheson  Graphite. 

Write  us  for  samples  for  test,  prices,  or  any  further  in- 
formation desired. 

INTERNATIONAL  ACHESON  GRAPHITE  COMPANY 

NIAGARA  FALLS,  N.  Y.,  U.  S.  A. 


fNPEPENDENT    OF     ALL    COMBINATIONS 

EAGLE 

WHITE  LEAD 

COMPANY 

15,000 

1008  to  1030  Broadway Cincinnati,  O. 


Corroders  by  the  "Old  Dutch  Process" 

PURE  WHITE   LEAD,  DRY  AND  IN  OIL 
RED    LEAD.  LITHARGE,  AND  ORANGE  MINERAL 


OFFICES   AND    WAREHOUSES: 

NEW   YORK   CITY, 54  MAIDEN   LANE 

AUSTIN  REMSEN,  Manager. 

PHILADELPHIA,      .         ,         .         .         .       142  N.  FOURTH  STREET 

T.  E.  BANNAN,  Manager. 

BALTIMORE,  .        ,         .         .         .  -     .     447  NORTH  STREET 

GEO.  O.  SHIVERS,  Manager. 

BUFFALO,         j         .         .         .         .  16  BUILDERS'  EXCHANGE 

A.  S.  GOLTZ,  Manager. 

PITTSBURQ .         .         .         . 

PITTSBURG  PAINT  SUPPLY  CO.,  Agents. 

CLEVELAND, 

A.  T.  OSBORN  CO.,  Agents. 

CHICAGO,          ,        „         t         .          125-127  NORTH  PEORIA  STREET 

E.  B.  BENNETT,  Manager. 

ST.  LOUIS 706  N.  ELEVENTH  STREET 

F.  L.  POWERS,  Manager. 

KANSAS  CITY,         ....  1012=14  WALNUT  STREET 

w.  R.  MCDONALD,  Agent. 

NEW  ORLEANS,     ....  308=310  GRAVIER  STREET 

JNO.  R.  TODD  &  BRO.,  Agents. 

8 


LOWE  BROTHERS  PREPARED 
LINSEED     OIL     PAINTS 

FOR  THE  PRESERVATION  AND  PROTECTION  OF 
STEEL  IN  BUILDINGS,  BRIDGES,  RAILWAY 
EQUIPMENT  AND  GENERAL  MANUFACTURING 

THE  ACKNOWLEDGED  "HIGH  STANDARD" 


Among  these  products  are  included: 

RED  LEAD  METAL  PRESERVA- 
TIVE (two  colors). 

BLACK    METAL  COATING 
No.  1407. 

GRAPHITE  PAINTS. 
CARBON  PAINTS  (four colors). 

OXIDE  OF  IRON  PAINTS  (three 
colors). 


All  are  Linseed  Oil  Paints  with  selected  pig- 
ments only.  They  are  made  from  legitimate  ma- 
terials and  based  upon  the  theory  that  the  solids 
are  coefficient  with  the  liquids  in  producing  the 
best  results,  and  that  their  quality  is  as  depend- 
ent upon  their  physical  as  upon  their  chemical 
structure. 

The  principles  upon  which  they  are  made  and 
used  are  fully  discussed  in  "Hints  on  Painting 
Structural  Steel",  "Suggestions  for  Specifications" 
etc.  Sent  on  application. 


THE  LOWE 
BROTHERS 
COMPANY 

DAYTON,  O. 
NEW  YORK 
CHICAGO 
KANSAS  CITY 


UNIVERSITY  OF  CALIFORNIA  LIBRARY 
BERKELEY 


THIS  BOOK  IS  DUE   ON  THE  LAST  DATE 
STAMPED  BELOW 

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50c  per  volume  after  the  third  day  overdue,  increasing 
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demand  may  be  renewed  if  application  is  made  before 
expiration  of  loan  period. 


&&i  i  -.:v 


REC'D  L.D 

JUN7    1963 


